Sayyiduna Uthman bin Affan (may Allah be pleased with him) narrates that a man came to the Noble Prophet (peace and blessings be upon him) and said: O Messenger of Allah! I performed the prayer but (became forgetful), so now I do not know whether I have prayed an even number of rak‘ahs or an odd number? The Prophet (peace and blessings be upon him) said: I warn myself against this, that Satan should begin to play with you in your prayer. If any one of you performs the prayer and does not know whether he has prayed an even number of rak‘ahs or an odd number, then he should perform two prostrations; through them his prayer will be completed.