When is the prostration for forgetfulness prescribed?

Question:
May Allah reward you with good, and may He do you good. When is the prostration for forgetfulness obligatory? Is it before the closing salam or after it?

Answer:
If one adds to the prayer, the prostration for forgetfulness is prescribed. If one adds to the prayer, or omits from it out of forgetfulness, or doubts in it—whether doubting the number of rak'ahs, or doubting the performance of an obligatory act, or something similar—then the prostration for forgetfulness is obligatory in three cases. In three cases, yes. If one adds to the prayer out of forgetfulness, or omits from the prayer out of forgetfulness, or doubts in the prayer generally, after he has performed what was omitted from the prayer—if he left off a rak'ah or more, or left off a pillar of a rak'ah, which is like leaving off the rak'ah—he performs what was omitted, then prostrates for forgetfulness. As for if he left off an obligatory act, the prostration for forgetfulness compensates for it. If he left off an obligatory act out of forgetfulness, the prostration for forgetfulness compensates for it. Likewise, if he doubts, he builds upon certainty, which is the lesser amount, and completes his prayer, then prostrates for forgetfulness. Yes.