What should one do who doubts a rak'ah of his prayer after finishing it, or doubts performing a pillar that has already passed?

Doubt concerning the performance of a pillar (rukn) of prayer necessitates its performance. So, whoever doubts having performed the bowing (rukūʿ), the default is that he has not bowed. And if he doubts the number of prostrations (sujūd), the default is that he has pro

strated only once. If doubt occurs after commencing the recitation of the next rakʿah, then the rakʿah in which the pillar was forgotten is nullified, and the current rakʿah takes its place. However, doubt after completing the prayer holds no significance. This ruling applies to a normal person, but as for one afflicted with obsessive whispers (waswās), he should not pay attention to his whispers.