The Ruling on Doubt in Prostration

Question:
A man doubts in his prayer, specifically regarding one of the rak'ahs, and does not know whether he prostrated twice or only once. What is required of him? Does he have to perform the prostration for forgetfulness? And where should the prostration for forgetfulness be performed in this case, before the taslim or after it? What do you advise one who is prone to frequent doubts and obsessions in his prayer? May Allah reward you with good.

Answer:
If his doubt arises after the prayer, meaning after the salam, and the doubt occurs to him then, his prayer is valid, and he does not have to perform the prostration for forgetfulness. However, if the doubt occurs during the prayer, he should perform the prostration and build upon certainty. If he doubts whether he prostrated once or twice, he performs the second prostration, whether in the first, second, third, or fourth rak'ah. He then performs the prostration for forgetfulness before the salam. If he prostrates after the salam, there is no harm, but it is better to do so before the salam. As for if his doubt arises after the prayer, once he has finished it, and the doubt occurs to him then, this is from obsessions and he should not pay attention to it. Doubt after the prayer has no effect.