A person performed his salaat, and after some time he realized that a sajda sahw which had become wajib in the salaat was not performed. What should he do in this case? Also, what is the ruling if the sajda sahw was left out intentionally?
Sajda sahw, if left out (forgetfully or intentionally), should be performed as long as the time for that salaat remains, and as long as a person does not do any act that can prevent him from the continuation of a salaat after the salaam. (e.g. Talking, Eating, Laughing, Turning ones chest away from the Kaaba, or a long duration of time after the salaam).
However, if any of these acts were done intentionally, then it would be wajib to repeat the salaat as long as the time of that salaat has not terminated. On the other hand if any of the acts were done while forgetting that it was wajib or the time for that salaat has terminated, then he would be excused from repeating the salaat.
(Kitaabus-Salaah – Pg. 169 / Shaami – Vol. 2 – Pg. 79 / Tahtawi – Pg. 252 / Imdadul Fatawa – Vol. 1 – Pg. 366 / Fatawa Darul Uloom Deoband – Vol. 4 – Pg. 384 / Imdadul Fatawa – Vol. 1 – Pg. 366).
And Allah knows best.
Mufti Waseem Khan