Doubt: If one’s suspicion prevails, he acts according to what prevails in his mind and prostrates for forgetfulness after the salam.

The Shaykh : As for doubt, it is hesitation, such as when one doubts whether he prayed three or four rak'ahs. We ask him, “Which one prevails in your mind?” If he says, “It prevails in my mind that I prayed three,” we tell him, “Complete the fourth and prostrate for forgetfulness after the salam.” If he says, “It prevails in my mind that I prayed four,” we tell him, “Your prayer is now complete, and prostrate for forgetfulness after the salam.”