It is narrated from Sayyiduna Abdullah bin Mas’ud (may Allah be pleased with him), he says: The Messenger of Allah (peace and blessings be upon him) led a prayer, I do not remember whether there was an addition or a deficiency. When the Prophet (peace and blessings be upon him) finished the prayer with salam, someone said: O Messenger of Allah! Has something new been prescribed in the prayer? He (peace and blessings be upon him) said: (No, and what is it (that you are sensing)? The people said: You led such and such number of units in the prayer. So the Prophet (peace and blessings be upon him) folded his legs and performed two prostrations of forgetfulness (sahw), then when he finished with salam, he said: I am only a human being, just as you forget, I also forget. When any of you is in doubt during the prayer, he should seek (the correct number of units in the prayer), and when he finishes with salam, he should perform two prostrations.