What should the worshiper do if he forgets a prostration in congregational prayer with the Imam, or doubts that he only prostrated once, whether he remembers after the Imam raises his head from the second prostration?

If the ma'mum (follower in prayer) doubts whether he performed one prostration or two, he should assume the lesser number, making it one, unless it is a case of waswas (obsessive doubt). If he forgets a prostration or falls behind the Imam in it due to a valid excuse other than negligence, he should perform what he missed and then continue to follow the Imam in the remainder of the prayer. In this situation, the ma'mum is not required to perform the prostrations of forgetfulness (sujud al-sahw) because the Imam bears the burden of his forgetfulness.