Q: What are the causes for Sujud-ul-Sahw (Prostration of Forgetfulness) in Salah (Prayer)? Please discuss this subject in detail. May Allah reward you.
A: The reasons for Sujud-ul-Sahw may be because an addition to Salah or a omission therefrom. The Prophet (peace be upon him) offered Sujud-ul-Sahw in a number of cases in which some acts relating to Salah slipped his mind (peace be upon him). For instance, he (peace be upon him) offered Sujud-ul-Sahw when he forgot to sit for the first Tashahhud (testification recited in the sitting position in the second unit of Prayer) and stood directly for the third Rak`ah (unit of Prayer); at that time, he offered two Sujuds before Taslim (salutation of peace ending the Prayer). He (peace be upon him) also offered Sujud-ul-Sahw after Taslim when he performed a four-Rak`ah Prayer as a two- Rak`ah one out of forgetfulness. In that situation, when he was notified of that slip, he completed Salah and then offered Sujud-ul-Sahw after Taslim. At other time, he forgot and offered a three-Rak`ah Salah instead of a four-Rak`ah one, and when he was reminded of that, he performed the fourth Rak`ah and then offered Sujud-ul-Sahw after Taslim. Sometimes, he (peace be upon him) obliviously added a fifth Rak`ah to the four-Rak`ah Salah, and when his attention was directed to this, he offered Sujud-ul-Sahw after Taslim. He (peace be upon him) said in this regard: I am a human being like you and liable to forget like you. Therefore, if I forget, remind me.
Accordingly, Sujud-ul-Sahw is attributed either to a reduction from Salah or an addition thereto as referred to above. If an Imam (the one who leads congregational Prayer) has added a Rak`ah, Ruku` (bowing), or Sujud (prostration) out of forgetfulness, the Ma'mums (persons being led by an Imam in Prayer) should draw his attention to that mistake, and the Imam should respond to their notice by offering Sujud-ul-Sahw before or after Taslim, unless he is certain of the correctness of what he has done. It is preferable that Sujud-ul-Sahw be offered before Taslim in all cases of forgetfulness, unless the latter is related to reducing one or more Rak`ah. In this case, Sujud-ul-Sahw is to be preferably offered after Taslim. Likewise, when the worshipper has forgotten how many Rak`ahs they has offered and completed Salah according to the number of Rak`ahs they are surer they have offered, they should also offer Sujud-ul-Sahw preferably after Taslim. It is reported on the authority of Ibn Mas`ud (may Allah be pleased with him) that the Prophet (peace be upon him) said: If one of you has doubts their Salah [how many Rak`ahs they have offered], they should follow what they think to be right, complete Salah accordingly, make Taslim, and then offer two Sujuds [of forgetfulness]. This means Sujud-ul-Sahw is to be done after Taslim in this case. In light of the above, it becomes clear that it is Mashru` (Islamically prescribed) to offer Sujud-ul-Sahw when they absentmindedly adds or omits anything from Salah.
If they, for instance, forget to offer Sujud, Ruku`, or one or more Rak`ahs, they are to be notified of their mistake, return to what is right, complete their Salah accordingly,
and then offer Sujud-ul-Sahw before Taslim, except in two cases in which it should be offered after Taslim: when the worshipper makes Taslim before they have offered one Rak`ah or more they have obliviously omitted and when the worshipper has doubts about how many Rak`ahs they have offered but mostly think of a certain number of Rak`ahs to have preponderance over another number. In this case, they have to complete their Salah according to that thought, offer Taslim, and then perform Sujud-ul-Sahw. However, if the worshipper has doubts about how many Rak`ahs they have performed without thinking mostly of a certain number to have preponderance in this regard, they have to complete Salah according to the lesser number and then offer Sujud-ul-Sahw before Taslim, as the Prophet (peace be upon him) said in the Hadith narrated on the authority of Abu Sa`id (may Allah be pleased with him) that: If one of you has doubts during their Salah and does not know if they have offered three or four [Rak`ahs], let them remove their doubt, complete Salah accordingly and then make two Sujuds before Taslim. If they have offered five Rak`ahs, they [i.e., the two Sujuds] would make their Salah even and if they have completed the four Rak`ahs [when they have finished], they [i.e., the two Sujuds] would be in defiance of the devil.(Related by Muslim in his Sahih [Authentic Hadith Book]) This is Mashru` and Wajib (obligatory) on each Mu'min (believer), male and female, to do upon forgetting any act of Salah.
If the worshipper has some doubts during Salah and does not side with a certain thought related to what exactly they have performed, they should build on the amount they are certain to have performed, i.e., the lesser amount, and complete their Salah accordingly to be on the safe side. For example, if the worshipper does not know whether they have performed one or two Sujuds or two or three Rak'ahs, they should consider it to be just one in the former and two in the latter, offer the second Sujud or the third Rak'ah and complete their Salah as usual. Building on the lesser amount puts the worshipper on the safe side regarding Salah. If the worshipper has realized the mistake and made up for it during Salah (before Taslim), they should say Takbir (saying: "Allahu Akbar [Allah is the Greatest]") and offer Sujud-ul-Sahw exactly like the normal Sujud performed during Salah, saying thrice in each Sujud: 'Subhana Rabbiya Al-A`la (Glory be to my Lord, the Most High)' and supplicating Allah as done in the ordinary Sujud, and then say Taslim. However, if the worshipper sides with a certain thought in preponderance over the other regarding the doubt about how many Rak`ahs or Sujuds they have performed, they should build their Salah on the thought they side with. For instance, if the worshipper has doubts whether they have offered two or three Rak`ahs, but they think performing three has preponderance over two, they should make it three, complete their Salah accordingly, and offer Sujud-ul-Sahw after Taslim, unless he is an Imam whose attention has been drawn by the Ma'mums that he has forgotten some act of Salah, in which case, the Imam should respond, as the belief of a group is more certain than his belief. If the worshipper has forgotten to do something that is Mustahab (desirable) and not Wajib to be done during Salah, they are not required to offer Sujud-ul-Sahw. If, for instance, the worshipper has forgotten to raise their hands on Takbirat-ul-Ihram (saying: "Allahu Akbar [Allah is the Greatest]" upon starting Prayer) or upon Ruku`, or if they have performed Tawarruk (placing the left foot under the right leg and sitting on the posterior during the last Tashahhud) in the first Tashahhud, or Iftirash (placing the left foot to the side and sitting on it between the two prostrations, keeping the right foot vertical) in the last Tashahhud in the four- or three - Rak`ah Prayers, they are not required to offer Sujud-ul-Sahw, as it is not Wajib in such cases. However, there would be no problem if they offer it.
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