What is the prostration of forgetfulness (Sujud Al-Sahw), how is it performed, and when is its time? What is the ruling for one who doubts during their prayer, such as doubting whether they said "Subhana Rabbi Al-Azeem" or not, or doubting whether they prostrated or not? What should they do, and do they perform the prostration of forgetfulness?

The prostration of forgetfulness (Sujud Al-Sahw) consists of two prostrations by which the worshipper compensates for an increase, decrease, or doubt in their prayer. The worshipper builds upon certainty when in doubt and strives for correctness, performing the prostration of forgetfulness either before or after the salutations (taslim), depending on the situation. If one doubts having performed a pillar and remembers it before starting another pillar, they should perform it. If they remember it after that, they should build upon the rak'ah that followed the one with the deficiency. As for doubts regarding obligatory acts (wajibāt), if one remembers it while still in its proper place, they should perform it. If they remember it after having passed its proper place, they should not return to it but instead perform the prostration of forgetfulness. If one makes the salutations before completing the prayer, they should complete their prayer and then perform the prostration of forgetfulness. As for saying "Subhana Rabbiyal-Azeem" (Glory be to my Lord, the Most Great) in bowing (ruku'), it is considered obligatory by Imam Ahmad, and omitting it necessitates the prostration of forgetfulness. However, it is considered a Sunnah by the majority of scholars and does not necessitate the prostration of forgetfulness if omitted. As for prostration (sujud), it is a pillar, and its omission cannot be compensated for by the prostration of forgetfulness.