Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) narrates: The Prophet Muhammad (peace and blessings be upon him) either added something to the prayer or omitted something while leading us in prayer. So it was said: O Messenger of Allah (peace and blessings be upon him)! Has a new command regarding the prayer come? The Prophet (peace and blessings be upon him) said: If a new command had come, I would have informed you about it, but I am a human being; I forget just as you forget. So if any of you has doubt about his prayer, he should consider which situation is closer to being correct and complete his prayer on that basis, then say the salam and perform two prostrations of forgetfulness.