The ruling on one who doubts the number of prostrations

Question:
This questioner says: A man doubted in his prayer—meaning, in one of the rak'ahs—so he does not know whether he prostrated two prostrations or one prostration. What is obligatory for him? Does he prostrate for forgetfulness? And where is the prostration for forgetfulness in this case—before the taslim or after it? And what do you advise one who has many doubts and obsessions in prayer?
May Allah reward you.

Answer:
If his doubt occurred after the prayer, after he had said the taslim and finished, and the doubt came to him then, he does not act upon it. His prayer is valid, and praise be to Allah, and he owes no prostration for forgetfulness if his doubt was after the prayer—meaning, it only occurred to him after the prayer. In this case, he owes nothing.
As for if the doubt was during the prayer, he performs the prostration, building upon certainty. If he doubts whether he prostrated one prostration or two, he performs the second prostration, whether in the first rak'ah, or the second, or the third, or the fourth. He prostrates for forgetfulness before the salam. If he prostrates after the salam, there is no harm, but in such a case, it is better to do it before the salam.
As for if his doubt was after the prayer, and after he had finished it, and the doubt came to him then, this is from obsessions. He should not pay attention to it, and doubt after the prayer has no effect. Yes.

The presenter: May Allah reward you.