When does the prayer of the person suffering from obsessive doubts (al-waswasi) become invalid due to an excess (in actions), and is there a consensus on this? And what if he is negligent and his mind wanders during prayer, and he cannot remember whether he prostrated or not due to lack of devotion and concentration? And is what Al-Zuhayli stated – regarding building upon the lesser (number of units) if one cannot determine the correct one – a consensus?

The basic principle is that whoever doubts in their prayer should build upon the minimum [number of units], unless this becomes frequent and turns into whispers (waswasa). In that case, they should ignore the doubt and not pay attention to it, and there is no prostration of forgetfulness (sujud as-sahw) upon them. The jurists of the four schools of thought and others have explicitly stated that a person afflicted with waswasa should disregard the whispers and not pay attention to them, because hardship is negated in Islamic law. So, if a person afflicted with waswasa disregards the whispers, their worship is sound. As for someone who is not afflicted with waswasa, they should build upon the minimum.