SAJDAH SAHW – PROSTRATION OF FORGETFULNESS & ITS METHOD

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SAJDAH SAHW – PROSTRATION OF FORGETFULNESS & ITS METHOD

TITLE 1: DEFINITION :

Allah the most merciful has granted us an easy method through which we can make up for some of our shortcomings or mistakes during Salah (prayer). This is done by making two extra prostrations (sujdah/sujood) and this is called Sajdah Sahw in arabic or prostrations of forgetfulness as translated in english. Please note that sajdah sahw is only to compensate for certain (some) mistakes during salah and not all or every mistake. This will be explained in detail in the below article In sha ALlah
Case 1.1: How is it done and How many times?
Sajdah sahw are two prostrations of forgetfullness. they are normal prostrations (sajdahs) like any other sajdah during salah/prayer.
E.g : In a normal salah, while praying , you first say Allahu Akbar then prostrate. then while getting up you say Allahu Akbar. pause for a moment and again say Allahu akbar to prostrate for the second time. Then while getting up you say allahu akbar.
Similarly sajdah sahw is to be done. But the timing for these sajdahs will be explained below. Go with the flow In sha allah Note : Irrespective of the number of mistakes we do in the salah the sajdah sahw is done only once at the end and not multiple times.

TITLE 2: For those who wish to learn about this topic in Urdu may visit the below two links :

Shaikh Uthaymeen’s book : http://www.islamhouse.com/p/76627
Shaikh Saleh al Munajjid’s fatwa in Urdu : http://islamqa.info/ur/ref/12527

TITLE : 3 CONDITIONS OR RULING WHEN ONE IS REQUIRED TO DO SAJDAH SAHW

1- Addition (i.e doing something extra) : for example, doing an extra bow (rukoo’), prostration (sujood), extra standing, sitting or etc.
2- Omission (i.e subtracting or Omitting something): such as omitting an essential part of the prayer, or omitting one of the obligatory parts of the prayer like not sitting after 2 rakats (in a 4 rakat prayer) and directly standing or missing a tashahud etc..
3- Being uncertain (shak/doubt): such as when a person is not sure how many rak’ahs he has prayed, whether it was three or four and similar kinds of mistakes

TITLE 4: IS DOING SAJDAH SAHU NECESSARY TO MAKE UP FOR THE MISTAKES?

Prophet (s.a.w) said “If any one of you forgets [something in the prayer], let him do two prostrations (Called as sajdah sahw).”
[Ref: Narrated by Muslim, 402]
Abu Huraira reported: The Messenger of Allah (may peace be upon him) said: When any one of you stands up to pray, the devil comes to him and confuses him to that he does not know how much he has prayed. If any one of you has such an experience he should perform two prostrations while sitting down (in qa’da).
[Ref: Sahih Muslim, Book 4, Hadith 1159]
Abdullah Ibn Abbas (r.a) said The Prophet (peace be upon him) named the two prostrations of forgetfulness disgraceful for the devil
[Ref: Sunan Abu Dawood, Book 3, Hadith 1020]

TITLE 5: SAJDAH SAHW IS APPLICABLE FOR ALL PRAYERS (FARDH, SUNNAH) EXCEPT SALATUL JANAAZAH

The first proof which helps us understand that the command of sajdah sahw is a general command applicable for all prayers is the following ahadeeth:
Prophet (s.a.w) said “If any one of you forgets [something in the prayer], let him do two prostrations (Called as sajdah sahw).”
[Ref: Narrated by Muslim, 402,Also see 572j]Narrated Abu Huraira: Allah’s Messenger (sallallahu ‘alaihi wa sallam) said, “When anyone of you stands for the prayers, Satan comes and puts him in doubts till he forgets how many rak`at he has prayed. So if this happens to anyone of you, he should perform two prostrations of Sahu while sitting.
[Sahih al Bukhaari, Vol. 2, Book 22, Hadith 324]
Secondly Imam Bukhari (r.h) – the Ameer ul Mumineen fil Hadeeth, has titled a chapter in his book (Sahih Al Bukhari) calling it : باب السَّهْوِ فِي الْفَرْضِ وَالتَّطَوُّعِ i.e “Bab al-Sahw fi’l-fard wa’l-tatawwu’ i.e Chapter on forgetfulness in obligatory and voluntary prayers) wherein he mentioned that Ibn ‘Abbaas (may Allaah be pleased with him) did two prostrations of forgetfulness after Witr,
Thirdly al-Haafiz Ibn Hajar (r.h) said in his book, al-Fath, commenting on the report of Ibn ‘Abbaas: this was narrated by Ibn Abi Shaybah with a saheeh isnaad.
The point of quoting what Ibn ‘Abbaas did is that Witr is not an obligatory (i.e. fardh) prayer , but Ibn ‘Abbaas nevertheless did sujood al-sahw in it, which indicates that sujood al-sahw should be done in both obligatory and naafil prayers as well.

TITLE 6: THE PILLARS (ARKAAN) AND WAAJIBAAT OF SALAH

Pillars (Arkaan) : Essential acts of salah without which the salah is null and void
As mentioned in the beginning, sajdah sahw cannot be done to compensate for everything. It is acceptable as a compensation only for certain minor mistakes and not for any or major mistakes.
In the case of forgetting or leaving out any of the essential pillars (arkaan) of the prayers the sajdah sahw will not compensate for it. One has to go back or re-do the missed pillar and then do the sajdah sahw. The obligatory pillars constitute :
1 – Praying being in a state of purity (wudhu and being free from sexual/menstrual discharge. Breaking wind also invalidates the purity)
Ibn ‘Umar (radhiAllaahu ‘anhumaa) said: Indeed I heard Rasoolullah (sallallaahu ‘alaihi wa sallam) say: Allaah does not accept Prayer without purification (Wudho or when required then – Ghusl), nor Sadaqah from illegally attained wealth. [Muslim (1/160) and others]
“The key to prayer is purification; its beginning is Takbeer and its end is Tasleem” [Sunan Abu Dawood (61, 618), al-Tirmidhee (3, 238), Ibn Maajah (275, 276) on the authority of `Alee bin Abu Taalib, Abu Sa`eed al-Khudree رضي الله عنهما and graded as “Saheeh” by Shaikh al-Albaanee]
To know what invalidates the wudu’ and the proper method of doing wudu’ as per Sunnah visit: http://the-finalrevelation.blogspot.com/2012/07/wudhu-ablution.html
2 – Intention (in your heart and not verbally speaking it out) so as to which prayer are you praying
3 – Facing the Qiblah (except during praying a nafil salah during travel or in the case when one cannot determine the qiblah at all)
The evidence: The saying of Allaah: { And stand before Allaah with obedience } [Al Baqarah: 238]
The evidence from the Sunnah: The Messenger’s order – صلى الله عليه وسلم – to ‘Imraan ibn al Husayn – may Allaah be pleased with him: “…pray standing…” [Collected by al Bukaaree: 1/264 #1117]
Refer to: Sifat Salaat an Nabee by al Albaanee P.77, Fiqh al ‘Ibaadaat by Shaykh ibn ‘Uthaymeen : P.131, al Mulakhas al Fiqhee by Shaykh Saalih al Fawzaan : P.100.
4 – beginning the prayer by raising the hands and saying Takbirat-ul-Ihram (saying: Allahu Akbar [Allah is the Greatest] upon starting Prayer).
The evidence: “…then face the Qiblah and perform the Takbeer…” [Collected by al Bukaaree: 1/178 #793 and Muslim: 1/82: #397]
“The key to prayer is purification; its beginning is Takbeer and its end is Tasleem” [Sunan Abu Dawood (61, 618), al-Tirmidhee (3, 238), Ibn Maajah (275, 276) on the authority of `Alee bin Abu Taalib, Abu Sa`eed al-Khudree رضي الله عنهما and graded as “Saheeh” by Shaikh al-Albaanee]
5 – Having Tuma’neenah (tranquility and khushu in each position (posture) of the prayer)
The prophet (s.a.w) has warned us severely to keep our back (spine) straight (such that if water were to be poured over it, it would not stirr down instantly) during rukoo’ and to prostrate properly touching the seven body parts during sujood, to sit and stand and bow such that our bones are set and still. There is a hadeeth wherein a man who prayed quickly or hurriedly and the prophet (s.a.w) asked him to pray again and again. The below ahadeeth explains this :
It was narrated from Hudhaifah that: He saw a man praying (And his bowing and prostration) were lacking. Hudhaifah said to him: ‘For how long have you been praying like this?’ He said: “For forty years.’ He said: ‘You have not been praying for forty years and if you die praying like this, you will have died following a path other than the path of Muhammad (s.a.w). Then he said: ‘It is possible for a man to pray briefly (shortly/quickly), but still do it properly.”
[Ref: Sunan an-Nasa’i 1312; Also see Sahih al-Bukhaari Vol. 2, Book 13, Hadith 1313]
Abu Hurayrah (may Allaah be pleased with him) reported that a man entered the mosque whilst the Messenger of Allaah (peace and blessings of Allaah be upon him) was sitting in a far corner. He prayed, then he came and greeted him with salaam. The Messenger of Allaah (peace and blessings of Allaah be upon him) said, “Wa ‘alayka al-salaam, go back and pray, because you have not prayed.” So he went back and prayed, then he came back and greeted the Prophet (peace and blessings of Allaah be upon him), who said, “Wa ‘alayka al-salaam, go back and pray, because you have not prayed.” On the second occasion, or subsequently, the man said, “Teach me, O Messenger of Allaah.” He said, “When you stand up to pray, do wudoo’ properly, then face the qiblah and say Takbeer (‘Allaahu akbar’). Then recite whatever is easy for you of Qur’aan, then bow until you are at ease in rukoo’, then stand up until your back is completely straight. Then prostrate until you are at ease in sujood, then sit up until you are at ease in your sitting, then prostrate again until you are at ease in your sujood, then sit up again until you are at ease in your sitting. Do this in all your prayers.” (Reported by all; this version reported by al-Bukhaari, Fath, 6251).
Please see this link for further details and fatwas of scholars : http://www.islamweb.net/emainpage/index.php?page=showfatwa&Option=FatwaId&Id=180233
To know the different postures in the light of authentic hadeeth and how to pray salah step by step visit : http://the-finalrevelation.blogspot.com/2012/11/pray-salah-step-by-step-with-posture.html
6 – not missing/leaving out single or multiple rakah
The evidence for this will be enlisted below in the article showing that when the prophet (s.a.w) missed out rak’ahs, he made it up by re-praying those.
7 – not missing a sajdah or rukoo’
The evidence: { O you who have believed! Bow down, and prostrate yourselves, and worship your Lord and do good that you may be successful } [Al Hajj: 77]
“…then bow until you are tranquil…” [Collected by al Bukaaree: 1/178, #793 and Muslim: 1/82, #397]
“…then prostrate until you are tranquil…” [Collected by al Bukaaree: 1/178, #793 and Muslim: 1/82, #397]
8 – Rising from rukoo’
The evidence: “…then rise until you are tranquil…” [Collected by al Bukaaree: 1/178, #793 and Muslim: 1/82, #397]
9 – Sitting between two prostrations
The evidence: “…then rise from the prostration until you are tranquil…” [Collected by al Bukaaree: 1/178, #793 and Muslim: 1/82, #397]
10 – covering the awrah (the parts of the body that are compulsory to be covered during salah)
There is a unanimous agreement of scholars that for men, the awrah to be covered is from navel to knees and to cover his shoulders as well (unless he is too poor to afford such covering on his shoulder) and for women her entire body is awrah.
“Allaah will not accept the prayer of a woman who has started to menstruate, except with a khimaar (covering)” (Reported by Ahmad, Abu Dawud, Ibn Maajah and al-Tirmidhi, with a saheeh isnaad)
Abu Dawud reported from Umm Salamah that she asked the Prophet about a woman who prayed wearing a dir’ (chemise or upper garment) and a khimaar (head cover), but no izaar (lower garment). He said: “The woman is ‘awrah.”
As for the face, the Sunnah is to uncover it during prayer, so long as no non-mahram men are present. According to the majority of scholars, the feet must be covered; some scholars allow uncovering the feet but the majority say the opposite. Abu Dawud reported from Umm Salamah (may Allaah be pleased with her) that she was asked about a woman who prayed in a khimaar and qamees (dress or gown). She said, “There is nothing wrong with it if the dir’ (chemise) covers her feet.” In any case, it is better to cover the feet, to be on the safe side. As far as the hands are concerned, there is more leeway: there is nothing wrong with either covering them or uncovering them, although some scholars think that it is better to cover them. And Allaah is the Source of strength.
Fataawa al-Mar’ah al-Muslimah, by Shaykh ‘Abd al-‘Azeez ibn Baaz, p. 57
11 – Sitting for the final tashahud and sending the salaat and salaam upon the prophet (s.a.w)
The evidence: “…If you sit during the prayer say; at Tahiyaat liLaah…” [Collected by Muslim: 4/92, #402]
Sending the Salaat and Salaam upon the Messenger after the last Tashahhud.
The evidence for sending the salaat and salaam (known as durood ibraahim by most) :
The Hadeeth of Abu Mas’ood al Ansaaree – may Allaah be pleased with him. [Collected by Muslim: 4/98, #495 and an Nasaa-ee: P.220, #1283]
The Hadeeth of Ka’b ibn ‘Ajazah – may Allaah be pleased with him. [Collected by Muslim: 4/98, #406 and an Nasaa-ee: P.221, #1286]
The Hadeeth of Abu Humayd as Saa’idee – may Allaah be pleased with him. [Collected by al Bukhaaree: 3/216, #6360, Muslim: 4/99, #407 and an Nasaa-ee: P.222, #1291]
The Hadeeth of Abu Sa’eed al Khudree. [Collected by al Bukhaaree: 3/215, #6358 and an Nasaa-ee: P.222, #1290]
Refer to: Jalaa al Afhaam by ibnul Qayyim for the variations of the Salat and Salaam P.84, Kayfiyyat Salaat an Nabee by Shaykh ibn Baaz: P.11, Sifat Salaat an Nabee by al Albaanee P.164, Fiqh al ‘Ibaadaat by Shaykh ibn ‘Uthaymeen : P.132, al Mulakhas al Fiqhee by Shaykh Saalih al Fawzaan : P.104.
12 – Tasleem (saying As-salamu `alaykum warahmatullah on both the shoulders to end the prayer after completing the final tashahud)
The evidence:“The key to prayer is purification; its beginning is Takbeer and its end is Tasleem” [Sunan Abu Dawood (61, 618), al-Tirmidhee (3, 238), Ibn Maajah (275, 276) on the authority of `Alee bin Abu Taalib, Abu Sa`eed al-Khudree رضي الله عنهما and graded as “Saheeh” by Shaikh al-Albaanee]
The Hadeeth of ‘Abdullaah ibn Mas’ood: “He used to give Salaam to his right and to his left.” [Collected by Ibn Hibbaan: 5/329, #1990 and declared authentic by al Albaanee in al Irwaa #326]
The Hadeeth of Ibn ‘Umar – may Allaah be pleased with him. [Collected by an Nasaa-ee: P.227, #1320]
The Hadeeth of ‘Alqamah ibn Waa-il – may Allaah be pleased with him. [Collected by Abu Dawood and declared authentic by al Albaanee: 1/162, #797, as well as Muqbil in as Saheeh al Musnad: #1192]
The Hadeeth of Waa-il ibn Hajar. [Declared as authentic by al Albaanee in Tamaam al Minnah: P. 171]
[Also see : For Tasleem and Takbir al Ihram to be one of the obligatory pillars, see : Abu Dawud, Sunan, Book on purification, no. 61; Ibn Majah, Sunan, Book on purifacation and its Sunan, no. 275; Ahmad, Musnad, vol. 1, p. 123; and Al-Darimy, Sunan, Book on purification, no. 687]
13 – The following of these pillars in order
First Standing, then bowing, then rising, then prostrating, then sitting between the two prostrations, then prostrating again.
Refer to: Fiqh al ‘Ibaadaat by Shaykh ibn ‘Uthaymeen : P.132, al Mulakhas al Fiqhee by Shaykh Saalih al Fawzaan : P.104
14 – Reciting surah Al Faatiha
14.1 ) The Imam has to recite al faatiha otherwise his prayer is invalid. If he forgets to recite it for one rak’ah , he is to discard that rak’ah and start from the second or following rak’ah.
14.2) If a person prays Individually and knows al faatiha and omits it intentionally then his salah is invalid, if he does it unintentionally he has to make it up by reciting it first and then continuing with the salah. This point will be explained below under the title of timing to correct arkaan mistakes.
14.3) If a person is praying in a Jam’aat, then If a person does not read Surah Faatihah behind the Imaam or he catches up with the Imaam when he has already read Faatihah and bowed (rukoo’), then there is a difference of opinion among the Scholars as to whether his prayer is valid without Faatihah in this case or not. The most authentic and the safe opinion, which is also favored by most of the Sahaabah in this regard, is to repeat the rak’ah because of the report of the Prophet: ‘There is no prayer for the who does not recite Surah Faatihah’ while another version of this hadeeth adds, ‘there is no prayer for the one who does not recite Surah Faatihah behind the Imaam’. Although this later version is slightly weak but it is supported by other detailed evidences, which makes it obligatory for us to recite Faatihah behind the Imaam as well. And according to another opinion of the aslaaf, if he catches the rak’ah just before the rukoo’ i.e before the Imam gets up from rukoo’ , the his salah is valid and does not have to make up for the missed fatiha and there is a great detail of evidence on both sides.
Note: for those who are new to Islam and have not yet learned al faatiha, then for them they can recite or supplicate whatever is easy for them because of the evidence :
It was narrated that ‘Abd-Allaah ibn Abi Awfa said: A man came to the Prophet (peace and blessings of Allaah be upon him) and said: “O Messenger of Allaah, teach me something of the Qur’aan that will suffice me, for I cannot read.” He said, “Say: Subhaan-Allaah wa’l-hamdu Lillaah wa laa ilaaha ill-Allaah wa Allaahu akbar wa laa hawla wa la quwwata illa Billaah (Glory be to Allaah, praise be to Allaah, there is no god except Allaah and Allaah is Most great, there is no god except Allaah and there is no power and no strength except with Allaah).” The man made a grabbing gesture with his hand (indicating that he had learned a lot) and said, “This is for my Lord, what is there for me?” He said, “Say: Allaahumma ighfir li warhamni wahdini warzuqni wa ‘aafini (O Allaah, forgive me, have mercy on me, guide me, and grant me provision and good health).” He made another grabbing gesture with his other hand and stood up.
(Narrated by al-Nasaa’i, 924; Abu Dawood, 832. Its isnaad was classed as jayyid by al-Mundhiri in al-Targheeb wa’l-Tarheeb, 2/430. al-Haafiz Ibn Hajar indicated that it is hasan in al-Talkhees al-Habeer, 1/236)
Wajibaat (obligatory acts of salah)
The obligations of the prayer are the actions and statements in the prayer which render the prayer void if omitted intentionally. If omitted due to Sahw – forgetfulness/unintentionally, they are dropped [meaning they do not have to be made up] and one has to practice Sujood as Sahw in their place. They are:
The obligatory (or wajibat) parts of prayer, of which there are eight, as follows:
(i) Takbeers other than the opening takbeer or The Takbeerat from one state to another.They are every Takbeer in the Salaat other than Takbeeratul Ihraam at the beginning of the prayer
Refer to: al Mulakhas al Fiqhee by Shaykh Saalih al Fawzaan : P.105.
An example :
Questioner: When a man comes to the prayer and finds that the people are in rukoo’, is he to say two takbeers [i.e., saying ‘Allaahu Akbar’]—one for entering the prayer and another for going into rukoo’—or just one?
Al-Albaani: Two.
[Ref: Al-Hudaa wan-Noor, 428]
(ii) Saying “Sami’a Allaahu liman hamidah (Allaah hears those who praise Him” – for the imam and for the one who is praying alone.The evidence: The Hadeeth of Abu Hurayrah that when raising from Rukoo’, the Messenger used to say:
“Sami’ Allaahu liman Hamidah…” [Collected by al Imaam Muslim: 4/78 #392, an Nasaa-ee: #1060 and declared authentic by al Albaanee in Tamaam al Minnah: P. 190 ]
Refer to: Kayfiyyat Salaat an Nabee by Shaykh ibn Baaz: P.7, Sifat Salaat an Nabee by al Albaanee P.135, Fiqh al ‘Ibaadaat by Shaykh ibn ‘Uthaymeen : P.136, al Mulakhas al Fiqhee by Shaykh Saalih al Fawzaan : P.105.
(iii) Saying “Rabbana wa laka’l-hamd (Our Lord, to You be praise)”The evidence: The Hadeeth of ibn ‘Umar – may Allaah be pleased with him – that was collected by al Bukhaaree #736 and Muslim #390.
The Hadeeth of Anas – may Allaah be pleased with him – that was collected by Muslim #1411.
Refer to: Kayfiyyat Salaat an Nabee by Shaykh ibn Baaz: P.7, Sifat Salaat an Nabee by al Albaanee P.135, Fiqh al ‘Ibaadaat by Shaykh ibn ‘Uthaymeen : P.136, al Mulakhas al Fiqhee by Shaykh Saalih al Fawzaan : P.105.
(iv) Saying “Subhaana rabbiy al-‘azeem (Glory be to my Lord Almighty)” once when bowing
The evidence: The Hadeeth of Hudhayfah – may Allaah be pleased with him – that he heard the Messenger of Allaah – صلى الله عليه وسلم – saying while performing Rukoo’.
“…Subhaana Rabee al ‘Adheem …” [Collected by al Imaam Muslim: 6/50 #722]
The Hadeeth of ibn ‘Abbaas: “As for Rukoo’ – glorify Allaah the Mighty and Majestic during it…” [Collected by al Imaam Muslim: 4/166 #479]
Refer to: Kayfiyyat Salaat an Nabee by Shaykh ibn Baaz: P.6, Sifat Salaat an Nabee by al Albaanee P.132, Fiqh al ‘Ibaadaat by Shaykh ibn ‘Uthaymeen : P.136, al Mulakhas al Fiqhee by Shaykh Saalih al Fawzaan : P.105.
(v) Saying “Subhaana rabbiy al-a’laa (Glory be to my Lord most High)” when prostrating The evidence: The Hadeeth of Hudhayfah – may Allaah be pleased with him – that he heard the Messenger of Allaah – صلى الله عليه وسلم – saying while performing prostration’.
“…Subhaana Rabee al ‘Alaa …” [Collected by al Imaam Muslim: 6/50 #772]
Refer to: Kayfiyyat Salaat an Nabee by Shaykh ibn Baaz: P.8, Sifat Salaat an Nabee by al Albaanee P.145, Fiqh al ‘Ibaadaat by Shaykh ibn ‘Uthaymeen : P.136, al Mulakhas al Fiqhee by Shaykh Saalih al Fawzaan : P.105.
(vi) Saying “Rabb ighfir li (Lord forgive me or a similar dua’a) ” between the two prostrationsRefer to: Kayfiyyat Salaat an Nabee by Shaykh ibn Baaz: P.8, Sifat Salaat an Nabee by al Albaanee P.135, Fiqh al ‘Ibaadaat by Shaykh ibn ‘Uthaymeen : P.136, al Mulakhas al Fiqhee by Shaykh Saalih al Fawzaan : P.105.
(vii) The first tashahhudThe evidence: The Hadeeth of ibn Mas’ood – may Allaah be pleased with him that was collected by Muslim: 4/92 #402, an Nasaa-ee: #1159 and declared authentic by al Albaanee in as Silsilah as Saheehah : 2/583 #878.
Refer to: Kayfiyyat Salaat an Nabee by Shaykh ibn Baaz: P.11, Sifat Salaat an Nabee by al Albaanee P.160, Fiqh al ‘Ibaadaat by Shaykh ibn ‘Uthaymeen : P.136, al Mulakhas al Fiqhee by Shaykh Saalih al Fawzaan : P.105.
(viii) Sitting for the first tashahhudRefer to: Kayfiyyat Salaat an Nabee by Shaykh ibn Baaz: P.11, Sifat Salaat an Nabee by al Albaanee P.156, Fiqh al ‘Ibaadaat by Shaykh ibn ‘Uthaymeen : P.136, al Mulakhas al Fiqhee by Shaykh Saalih al Fawzaan : P.106.
NOTE: ANY RUKN (pillar) OR WAJIBAT(obligatory part) OF SALAH WHICH IS LEFT INTENTIONALLY, I.e ON PURPOSE THEN HIS SALAH IS NULL AND VOID AND HE HAS TO RE-DO THE LEFT OUT PORTION AND CONTINUE WITH THE SALAH OR RE-DO HIS SALAH AS PER DIFFERENT SITUATIONS
SIMILARITY AND DIFFERENCE BETWEEN ARKAAN (PILLARS/ESSENTIAL ACTS) AND WAJIBAAT (OBLIGATORY ACTS)
Similarity: Leaving out either deliberately (i.e on purpose) invalidates the salah.
Difference: The difference between a pillar (rukn – singular of arkaan) and an obligatory part (wajibaat) is that a pillar cannot be waived (i.e exempted or left out), whether one omits it deliberately or by mistake, rather it must be done or made up. Whereas an obligatory part is waived (exempted) if one forgets, and it can be compensated for by doing the prostration of forgetfulness (sujood al-sahw).
Extra info : To further study what are the obligatory pillars of salah and what are the sunnahs of salah visit the link : Obligatory and Sunnah Pillars of Salah

TITLE 7: SAJDAH SAHW BEHIND AN IMAM

CASE 7.1 : When the Individual prays with the Imaam from the start of the prayer
Sajdah Sahw is binding upon every Muslim who prays individually or one who leads others as an Imam. In other words, if one is praying individually then yes he has to make up for his mistakes during his salah, whereas if he is praying behind an Imam from the start till end, then the Imam bears his personal mistakes i.e there is nothing upon that individual.
If a person who is led in prayer by the Imam from the beginning of the prayer forgets anything in his prayer, he does not have to prostrate for forgetfulness because the Imaam acts on behalf of the people whom he leads in prayer, with the exception of one who neglects any of the obligatory elements of the prayer. So here when the Imam says the Tasleem (to end the prayer) the individual says so too and he does not have to do sajdah sahw here.
Ibn Qudaamah may Allaah have mercy upon him said: ‘If a person who is led in prayer (from start to end) forgets, then according to the correct opinion of the scholars may Allaah have mercy upon them he does not have to prostrate for forgetfulness.’
Al-Nawawi (may Allaah have mercy on him) said in al-Majmoo’ (4/63): If he makes a mistake when praying behind the imam, the imam carries his mistake, and neither of them should do the prostration of forgetfulness. There is no difference of scholarly opinion on this point.
Shaykh Abu Haamid said: This is the view of all the scholars except Mak-hool……
One is not allowed to do Sajdah sahw seperately when he is praying in a Jama’at because : :
Abu Hurairah reports that the Prophet (saws) said: “The imam is selected to be followed; therefore, do not differ with him. When he makes the takbir, (then) make the takbir, when he goes into ruku’, (then) make ruku’. When he says ‘Allah hears him who praises Him (Samiallah huliman hamidah),’ (then) say ‘O Allah, our Lord, to You belongs the Praise.(Rabbana wa lakal hamd)’ When he goes into sajdah, (then) make sajdah. If he prays sitting, then all should be sitting.”
[Ref : Sahih Muslim, Book 4, Hadith 826; Muwatta Malik, Book 3, Hadith 61; Sunan Al Nasai, Vol.2, Book1, Hadith 923; Sahih Bukhari, 1236 and others]
The above hadeeth means that one has to follow the Imam even with regards to sajdah Sahw. i.e if the Imam does sajdah sahw, you also should do it irrespective of you making a mistake or not.
There is a weak hadeeth reported on the Authority of Umar (r.a) which states “The one who is led in prayer (Muqtadi) does not have to make the two prostrations of forgetfulness (if he makes a mistake). But if the Imam himself forgets, both the Imam and those praying behind him must make the two prostrations ” [Reported in Bulugh Al Maraam of Ibn Hajar : Chapter 7 Sujud As Sahw , Hadith no. 361 and elsewhere. The matan (content) of the hadeeth is saheeh though as it has corroborating evidences]
The former hadeeth of Sahih Muslim mentioned above the latter one, also teaches us that one should not race with the Imam or precede him. One has to do things After the Imam and not before him or with him. Hence if the Imam makes a mistake then it is his duty to do the sajdah sahw and by doing this he will make up the mistakes of his as well those who are following him. If incase he doesn’t do sajdah sahw, then the muqtadi (follower) has to follow him and there shall be no sin on the follower because :
Narrated by Abu Huraira – Allah’s Messenger (saws) said, “If the Imam leads the prayer correctly then he and you will (both) receive the (full) rewards, but if the imam makes a mistake (in the prayer) then you will receive the (full) reward for the prayer, and the sin will be his.”
[Ref: Sahih Bukhari Hadith Vol.1, Book 11, Hadith 663 ]
Case 7.2: When the individual joins the prayer late
Imam al-Nawawi (may Allaah have mercy on him) said in al-Majmoo’ (4/64): If he joins the prayer late, then he makes a mistake after the imam says the salaam, the imam will not carry it for him, because he is no longer following him. End quote.
It says in al-Mawsoo’ah al-Fiqhiyyah (8/206): If the person who joined the prayer late says the salaam after the imam by mistake, he should continue making up what he has missed of his prayer and do the prostration of forgetfulness. End quote.
Shaykh al-Sa’di (may Allaah have mercy on him) said:
If he joined the prayer late and he makes a mistake in the part of the prayer that he is making up, then he has to do the prostration of forgetfulness. End quote. [Fataawa al-Sa’di (157).]
Shaykh Ibn ‘Uthaymeen (may Allaah have mercy on him) said in Majmoo’ al-Fataawa (14/ no. 698): If the person praying behind the imam makes a mistake in his prayer, and he joined the prayer late, he has to do the prostration of forgetfulness if his mistake is one that requires the prostration of forgetfulness. End quote.
Conclusion for title 7:
1) If a person joins the Imam from the begining of his salah, then he does not have to do sajdah sahw for his wajibaat (obligatory) mistakes only and has to follow the Imam.
2) If a person joins the Imam late , then if he makes a mistake after the Imam says tasleem, then he has to make up for it for he is now completing the left our salah on his own.

TITLE 8 : THE TIME TO CORRECT THE MISTAKE DURING SALAH

It is recorded from al-Mughirah ibn Shu’bah, that the Prophet sallallahu alehi wasallam said: “If one of you (in a 3 or 4 rakat prayer) stands after two rak’at (forgetting to sit for the first tashadud) and he has not completely stood, then he should sit (i.e if he remembers his mistake before completely standing straight with his spine being upright then he should sit back continuing the tashahud) but If he is already completely standing (and thereafter he remembers his mistake), he should not sit , (rather he should continue the prayer) and he should make two sujood of forgetfulness
[Re: This is supported by Ahmad, Abu Dawud, and Ibn Majah]
Case 8.1: Timing to Correct Wajibaat (obligatory) mistakes :
Shaikh Ib Uthaymeen (r.h) says in Majmoo’ Fataawa al-Shaykh, 14/14-16 :
Omitting an obligatory part (i.e wajibaat or obligatory part) of the prayer – such as if he omits an obligatory part and moves on to the next part of the prayer. For example, he forgets to say Subhaan Rabbiy al-A’la (Glory be to my Lord Most High) and he does not remember until he has got up from prostrating. In this case he has omitted an obligatory part of the prayer by mistake, so he should carry on with his prayer then do the prostration of forgetfulness before saying the salaam, because when the Prophet (peace and blessings of Allaah be upon him) omitted the first tashahhud he carried on with his prayer and did not go back and repeat anything, then he did the prostration of forgetfulness before saying the salaam. End Quote
Another example is that If a person after two rak’at, was about to stand for the third without sitting for the tashahud, such that he hasn’t completely stood up i.e straighten his spine, then he is to go back to sitting and completing the first tashahud.
If in case he has completely stood up once, then it is forbidden to go back to the tashahud position and rather he should continue his salah and make up for this wajibaat (obligatory) mistake by sajdah sahw as will be explained below.
Al-Mughni, authored by Ibn Qudaamah may Allaah have mercy upon him reads, :
“If one forgets something among the obligatory (waajibat i.e obligatory) mention/acts [such as Adhkaar], like the Tasbeeh in the bowing down position [Rukoo’] and in the prostration [Sujood], and saying ‘Rabi Aghfir li’ between the two prostrations, and the saying of ‘Rabana walaka Al-hamd’, then he should not go back to them once he has moved from the position where he should say it; rather, he should continue [his prayer] and prostrate for forgetfulness because of leaving it, by analogy to leaving the Tashahhud.”
Case 8.2: Timing to Correct a Rukun (Pillar) mistake:
There is no compromise in these mistakes for they are the pillars of salah. If one realizes WHILE MISSING/ERRING in a Rukn, then he is to stop doing what he’s doing and continue by re-doing the Rukn or properly doing the Rukn. If the person makes a mistake by completely leaving a Rukn and realizing it later , then he is to re-do the missed Rukn from the later position. the below phrase will help explain this.
Shaikh Ib Uthaymeen (r.h) says in Majmoo’ Fataawa al-Shaykh, 14/14-16 : (content order modified by this article’s compiler for better understanding of the readers)
In the case of omitting something, if a person omits one of the essential parts (i.e Rukn/pillar) of the prayer, one of the following two scenarios must apply:
(Scenario a) Either he remembers it before he reaches the same point in the following rak’ah, so he has to go back and do that essential part of the prayer and whatever came after it,
An example for scenario a : a man stood up after doing the first prostration of the first rak’ah and did not sit or do the second prostration. When he started to recite Qur’aan he remembers that he had not done the second prostration or sat between the two prostrations. In that case he should go back and sit as between the two prostrations, then prostrate, then stand up and do whatever is left of his prayer, and do the prostration of forgetfulness after saying the salaam.
(Scenario b) Or he does not remember it until he reaches the same point in the following rak’ah, in which case the following rak’ah takes the place of the one in which he omitted that essential part, and he should make up the invalid rak’ah.
An example for scenario b : For one who did not remember until after he reached the same point in the following rak’ah is a man who stood up following the first prostration in the first rak’ah and did not do the second prostration or sit between the two prostrations, but he did not remember that until he sat between the two prostrations in the second rak’ah. In this case he should make the second rak’ah the first rak’ah, and add another rak’ah to his prayer, then say the salaam then do the prostration of forgetfulness.
In either of these two cases, he should do the prostration of forgetfulness after saying the salaam.

TITLE 9: FORGETTING TO DO SAJDAH SAHW AND ITS IMPACT ON THE VALIDITY OF SALAH

1) With regards to making a mistake in the arkaan (pillars) of salah, then the person has to not only make up the missed pillar (by re-praying or performing the missed pillar see case 8.2 under title 8 above for a detailed ruling) but also has to do sajdah sahw , failing to which his salah will be invalid. I.e under any circumstances, he has to make up for it otherwise his salah is not valid.
2) With regards to obligatory (wajibaat) mistakes then in that case if he FORGETS to do the sajdah sahw, but remembers it much later (say 30 mins), then according to one opinion of scholars he is to do the sajdah sahw whenever he remembers it and as per another opinion of scholars , even if he doesn’t do it due to forgetting , then his salah is valid. But if this is left out on purpose, i.e sajdah sahw is not done deliberately, then salah is invalid and this third point will be explained below in the words of scholars:
Shaykh Ibn ‘Uthaymeen was asked about a man who forgot the first tashahhud, and he knew that he had to do the prostration of forgetfulness before the salaam, but he forgot and said the salaam. What is the ruling? He replied: If he remembers within a short time, he should do the prostration, but if a long time has passed, then it is waived, such as if he did not remember until after a long time, if he had left the mosque then he does not have to go back to the mosque, and it is waived in his case. End quote. [Fataawa Ibn ‘Uthaymeen (14/50). ]
One of the opinions of Imam Ahmad ibn Hanbal, where he also said regarding this same case : “He (the person) should do the sujood even if the time that has passed is long, or he has spoken or left the mosque. This is also the opinion favoured by Shaykh al-Islam [Ibn Taymiyah]. Al-Ikhtiyaaraat al-Fiqhiyyah, p. 94.”
In Al-Rawd al-Murabba’ Sharh Zaad al-Mustaqna’ (2/461) it says: (If he forgets), i.e., he forgets to do the sujood al-sahw (for a minor mistake or a mistake apart from the arkaan i.e pillars of salah) which should be done before the salaam, (and he says salaam), then he remembers, (he should do the sujood) and it is obligatory (if the time that has passed is short)… If he has said salaam – and if a long time has passed according to what is ordinarily regarded as a long time (Added Note: say 15 minutes or more for e.g), or he broke his wudoo’, or he left the mosque – he does not need to do the sujood of sahw, and his prayer is still valid.
In Al-Sharh al-Mumti’ by Shaykh Muhammad ibn Saalih al-‘Uthaymeen (3/537), it says: The phrase ‘If he forgets and says salaam, he should still do the sujood if the time that has passed is short’ refers to the sujood that should be done before the salaam, (in case he forgets to do it before the tasleen then ) He should do this sujood if the time that has passed is short, otherwise (i.e if the time passed is long ) then he no longer has to do it, and his prayer is still valid.
An Example by Shaikh Saleh al Munnajid: A man may forget the first tashahhud , so he has to do sujood al-sahw before the salaam, but he forgets and says the salaam then If he remembers shortly afterwards, he should do the sujood of sahw, but if he remembers a long time afterwards, he no longer has to do it and his salah is valid End Quote. (because the first tashahud is not a pillar (Rukn) of salah)
Extract from shaykh zubair’s commentary on muwatta Malik:
If the Imam forgets in the prayer and then he forgets to perform the prostration of forgetfulness then according to Hakam Ibn Utba the people praying behind the Imam should perform the prostration of forgetfulness and according to Hamad Ibn Abi Sulayman they don’t need to perform it. (Musanaf Ibn Abi Shayba 2/39 hadith no.4525 and its chain is [Sahih] authentic)
It is established from the hadith of Abdullah Ibn Mas’ud (Radi Allahu Anhu) (Sahih Bukhari no.1226 and Sahih Muslim no.572) that if the Imam forgets to perform the prostration of forgetfulness then he should still perform it after doing the taslim (with the people who were praying behind him)
[Ref: http://www.salafiri.com/sharh-muwatta-imam-malik-shaikh-zubair-ali-zai-hadith-no-81-what-should-the-person-do-if-he-forgets-in-the-prayer/]

TITLE 10 : THE FOLLOWING ARE THE 3 DIFFERENT CASES WHEN AND HOW SAJDAH SAHW IS APPLICABLE.

Note:
1) refer Case 1.1 under title 1, to learn how sajdah sahw is enacted
2) Refer the timing section under title 8 above, to learn regarding the timing for correcting the mistakes for arkaan and wajibaat (obligatory) mistakes and they have been explained with examples therein. Please go through it before proceeding further as the timings for correcting the gesture/position are not mentioned below so to avoid confusion, understand and learn the timing from the above title thoroughly.
3) Please go through Title 9 above to learn the different situations when salah is valid if one forgets to do sajdah sahw and then proceed further.
THE DIFFERENCE OF OPINION AMONG SCHOLARS BOTH SALAF AND KHALAF
Imam al-Tirmidhi, in his Sunan, under the chapter titled باب مَا جَاءَ فِي سَجْدَتَىِ السَّهْوِ قَبْلَ التَّسْلِيمِ enlists the major difference of opinion among scholars and you can see a hint of these differences here : http://sunnah.com/tirmidhi/2#244
There is a narrated with another chain that Abu Hurairah and [‘Abdullah bin] As-Sa’id Al-Qari’ would perform the prostrations of As-Sahw before the Taslim.
Abu ‘Eisa (i.e. Imam tirmidhi) said:
The Hadith of Ibn Buhainah is a Hasan [Sahih] Hadith, and this is acted upon according to some of the people of knowledge. It is the opinion of Ash-Shafi’i, he held the view that all prostrations for As-Sahw were to be performed before the Salam, saying: “This one abrogates the other Ahadith” and he mentioned that the last action of the Prophet (ﷺ) was according to this.
Ahmad and Ishaq said: “When a man stands up after two Rak’ah, then he performs the prostrations for As-Sahw before the Salam according to the Hadith of Ibn Buhainah.”
‘Abdullah bin Buhainah is ‘Abdullah bin Malik [so he is] Ibn Buhainah (because) Malik is his father and Buhainah is his mother.
I was informed of this by Ishaq bin Mansur from ‘Ali [bin ‘Abdullah] bin Al-Madini.
Abu ‘Eisa said: The people of knowledge differ over when a man is to perform the prostrations of As-Sahw, is it before the Salam or after it. Some of them thought that her performs them after the Salam. This is the view of Sufyan Ath-Thawri and the people of Al-Kufah. Some of them said he performs them before the Salam. This is the view of most of the Fuqaha among the people of Al-Madinah, like Yahya bin Sa’eed, Rabi’ah, and others. This is also the saying of Ash-Shafi’i.
Some of them said when he adds to the Salat, then it is after the Salam, and when he leaves something out, then before the Salam. This is the view of Malik bin Anas.Ahmad said: “Whatever is reported from the Prophet (ﷺ) about the prostrations from As-Sahw then it is acted upon in either case.” He saw that when one stands after Rak’ah then according to the Hadith of Ibn Buhainah, he is to perform the prostrations before the Salam. When he prays five for Zuhr, then performs the prostrations after the Salam, and if he says Salam after two Rak’ahs of Zuhr or ‘Asr then he performs the prostrations after the Salam. All of them are to be acted upon depending upon the case, and in the cases where nothing is reported from the Prophet (ﷺ), then two prostrations are performed for As-Sahw before the Salam.
Ishaq said the same as Ahmad about all of this, with the exception that he said that for every case of As-Sahw that is not mentioned from the Prophet (ﷺ), then if it is an addition to the Salat, then prostrations are performed after the Salam, and if it is something that was left out, then the prostrations are performed before the Salam.
Thus we have taken the following from the rulings derived by scholars such as Shaikh Saalih Al-‘Ubaylaan and others.
CASE 10.1 : ADDING SOMETHING TO THE SALAH
‘The Prophet (peace be upon him) lead them in the Dhuhr prayer or the ‘Asr prayer and gave the salutation (i.e. tasleem ) after two rak’ahs. Then he departed quickly from one of the doors of the mosque, and the people were saying that the prayer had been decreased (shortened). The prophet (peace be upon him) meanwhile, stood by a piece of wood placed in the mosque, leaning against it, as if he was angry. So a man stood and said, ‘O Messenger of Allaah, have you forgotten or has the prayer been reduced?’ So the Prophet of Allaah (peace be upon him) said, ‘I did not forget nor has it been reduced.’ So the man said, ‘Rather you have indeed forgotten.’ So the Prophet (peace be upon him) said to the Companions, ‘Is what he is saying true?’ They said ‘Yes’ So the Prophet (peace be upon him) went forward and prayed what remained of the prayer (i.e the remaining 2 rakats), and then he gave the salutation (tasleem) , then he prostrated twice (i.e called as sajdah sahu), then he gave the salutation (tasleem) again
[Ref: Sahih Bukhari 4040 & Sahih Muslim 572 & others]
Ibn Mas’ood said: “The Prophet led us in prayer and he performed five Rak’ahs (instead of 4 rak’ah). When he turned around after ending the prayer, the people whispered to one another. He said: “What is the matter?” They said: ‘O Prophet of Allaah! Has the prayer been increased ?’ He replied: “No”. They said: ‘You performed five Rak’ahs’. So, he stood up again and performed two prostrations for forgetfulness, and then, said Salaam (i.e. tasleem). After that, he said: “I am just a human being like you (i.e. I forget)”
[Ref: Narrated in Sahih Muslim Book 4, Hadith 1177; and another similar narrations are in Sahih Bukhari Vol.2 Book 22 hadith 317, Also in tirmidhi, abu dawood and etc ]
Ibrahim b. Suwaid-reported:
‘Alqama led us in the noon prayer and be offered five rak’ahs; when the prayer was complete, the people said to him: Abu Shibl, you have offered five rak’ahs. He said: No, I have not done that. They said: Yes (you said five rak’ahs). He (the narrator) said: And I was sitting in a corner among people and I was just a boy. I (also) said: Yes, you have offered five (rak’ahs). He said to me: O, one-eyed, do you say the same thing? I said: Yes. Upon this he turned (his face) and performed two prostrations and then gave salutations, and then reported ‘Abdullah as saying: The Messenger of Allah (may peace be upon him) led us in prayer and offered five rak’ahs. And as he turned away the people began to whisper amongst themselves. He (the Holy Prophet) said: What is the matter with you? They said: Has the prayer been extended? He said: No. They said: You have in fact said five rak’ahs. He (the Holy Prophet) then turned his back (and faced the Qibla) and performed two prostrations and then gave salutations and further said: Verily I am a human being like you, I forget just as you forget. Ibn Numair made this addition:” When any one of you forgets, he must perform two prostrations.
[Sahih Muslim, Book 4, Hadith 1177]
Adding (doing something extra) : Anything to the salah, such as an extra rak’ah, extra rukoo’ , extra sujood, extra tasleem (i.e in Zuhur, saying tasleem after the second rak’ah instead of doing it after the 4th rak’ah)
Sajdah Sahw is to be done for : Arkaan and wajibaat (obligatory) mistakes
Sajdah Sahw is to be done at : After Tasleem (concluding the prayer by saying Assalamu ‘Alaykum or Assalamu ‘Alaykum wa rahmatullahi on both the shoulders)
CASE 10.2 : OMITTING (substracting) SOMETHING TO THE SALAH
Omitting an obligatory part of the prayer – such as if he omits an obligatory part and moves on to the next part of the prayer. For example, he forgets to say Subhaan Rabbiy al-A’la (Glory be to my Lord Most High) and he does not remember until he has got up from prostrating. In this case he has omitted an obligatory part of the prayer by mistake, so he should carry on with his prayer then do the prostration of forgetfulness before saying the salaam, because when the Prophet (peace and blessings of Allaah be upon him) omitted the first tashahhud he carried on with his prayer and did not go back and repeat anything, then he did the prostration of forgetfulness before saying the salaam.
Narrated by ‘Abdullah bin Buhaina – Allah’s Apostle once led us in a prayer and offered two Rakat and got up (for the third Raka) without sitting (for the first tashahud which comes after the second Raka). Then the people also got up with him and when he was about to finish his prayer, we waited for him to finish the prayer with Taslim but he (didn’t say the taslim, instead he) said Takbir (Allahu Akbar) and performed two prostrations (normal way) while sitting and then he finished the prayer with Taslim (i.e saying Askm on both the shoulders to end the prayer)
[Ref: This is related by Bukhari Volume 2, Book 22, Number 315; Muslim, Tirmidhi, Abu Dawood and others]
Omitting (or subtracting) : Anything such as tashahud , adhkaar, rukoo’, rak’ah , etc
Sajdah Sahw is to be done for : Arkaan and wajibaat (obligatory) mistakes
Sajdah sahw is to be done at : Before Tasleem
CASE 10.3 : Being Uncertain or having doubts
And if he has doubt – he doesn’t know how many raka’aat he has prayed, whether three or four – he must build upon what he is certain of, and this is the lowest (of the choices),[i.e. if he has doubt as to whether he has prayed three or four, he should pick the least of the choices, which is three.] and then prostrate before the tasleem
Yahya related to me from Malik from Zayd ibn Aslam from Ata ibn Yasar that the Messenger of Allah, may Allah bless him and grant him peace, said, “If you are uncertain in the prayer and do not know whether you have prayed three or four rakas, then pray a raka and make two prostrations from the sitting position before the tasleem. If the raka that you prayed was the fifth, then you make it even by these two sajdas, and if it was the fourth, then the two prostrations spite Shaytan.”
[Muwatta Maalik, Book 3, Hadith 66]
Abdur-Rahman bi Awf narrated that he heard the Prophet (s.a.w) saying:
“When one of you becomes forgetful in his Salat so that he does not know if he prayed one or two, then let him consider it one. When he does not know if he prayed three or four, then let him consider it three, and let him perform two prostrations before he says the Tasleem.”
[Jami` at-Tirmidhi 398]
Narrated by ‘Ata ibn Yaasir : The Prophet (sallallahu ‘alaihi wa sallam) said: When one of you is in doubt about his prayer, and does not know how much he has prayed, three or four rak’ahs, he should pray one (additional) rak’ah and make two prostrations while sitting before giving the salutation. If the (additional) rak’ah which he prayed is the fifth one, he will make it an even number by these two prostrations. If it is the fourth one (i.e if he didn’t make a mistake), the two prostrations will be a disgrace for the devil.
[Sunan Abi Dawood, 1026, Sahih al Albaanee]
Being Uncertain of (or having doubts) : such as if he sat for tashahud or not, if he recited the wajib adhkaar or not, if he did rukoo’ or not, etc
Sajdah Sahw is to be done for : Arkaan and wajibaat (obligatory) mistakes
Sajdah sahw is to be done at : Before Tasleem
Note: One does not have to say the tashahud again after doing sajdah sahw rather he may immediately say the tasleem.

TITLE 11: WHAT IF I DID SAJDAH SAHU BECAUSE I INITIALLY THOUGHT I MADE AN ERROR BUT LATER REALIZED THAT I NEVER MADE A MISTAKE AT ALL?

Narrated on the Authority of Aboo Sa’eed al-Khudree (may Allâh be pleased with him) that the Prophet (peace be upon him) said, ‘If one of you doubts in his prayer and does not know how many he has prayed –whether it is three or four – then let him cast away the doubt and build upon what he is certain of . Then let him perform two prostrations (of sajdah) before giving the salutation. So if he has prayed five (i.e made a mistake), then they (the 2 prostrations of forgetfulness) will make his prayer even for him, and if he has prayed the full four (rak’ah or has prayed the complete salah without any mistake), then they (the 2 prostrations of forgetfulness) will be a humiliation for Satan.(as he failed to spoil the prayer of the Muslim)’
[Ref: Sahih Muslim]
The sentence ” then let him cast away the doubt and build upon what he is certain of ” also means that to consider the least of the options, i.e. when one is confused if he prayed the 3rd rak’ah or not, then let him continue his prayer from the 2nd rak’ah to be sure.
The sentence “And if he has prayed it completely then the two prostrations will be a humiliation for the Shaytaan.” means that the prayer remains valid nevertheless and the loss and humility is to the shaitan only

Conclusion :

1. Sajdah Sahw alone by itself cannot compensate for: a mistake done in a Rukn of salah, in the case of which the person has to make up for the missed Rukn and then do sahw
2. Sajdah sahw alone by itself can compensate for : wajibaat (obligatory) mistakes for which sajdah sahw at the end will suffice.
3. Sajdah Sahw has three different cases mentioned above under title 10.
Important Points to remember :
Memorize the arkaan and waajibat of the salah so you know what to do when. Also remember the difference cases mentioned above .
Sajdah Sahw can compensate only for wajibaat (obligatory) mistakes and not All mistakes such as the obligatory pillars of salah.
Sajdah Sahw insults the shaitan and is a mercy from Allah to help us correct our mistakes.
Sajdah Sahw is to be done ONLY once (2 prostrations) before or after tasleem (Depending upon the cases mentioned under title 10 above) to compensate for ALL THE ERRORS together at once. Meaning, if you made 4 mistakes in your Dhuhr prayer then you have to do sajdah sahw only once and not 4 separate times.
The timing to correct the mistakes should be remembered (see title 8 above)
To know more about Sajdah Sahw you may also contact us from the Contact us Page on the top RHS of the blog or you may leave a comment.
Here is an easy short article of shaykh zubair briefing this issue: http://www.salafiri.com/sharh-muwatta-imam-malik-shaikh-zubair-ali-zai-hadith-no-81-what-should-the-person-do-if-he-forgets-in-the-prayer/
All mistakes are Mine and All good is from Allah alone. May Allah have mercy on the one who corrects me.