Alqamah narrates: Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) reported this. Once, the Prophet Muhammad (peace and blessings be upon him) led the prayer. The narrator named Ibrahim says: I do not know whether the Prophet (peace and blessings be upon him) added to it or omitted something from it. When he finished the prayer with salam, it was said to him: 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: No. What has happened? The people said: You led the prayer in such and such a manner. The narrator says: The Prophet (peace and blessings be upon him) spread his leg, faced the qiblah, performed two prostrations of forgetfulness (sajda sahw), then finished with salam. Then he turned towards us and said: If a new command regarding the prayer had come, I would have informed you about it. But I am also a human being like you; I forget just as you forget. So when I forget, remind me. When a person is in doubt about his prayer, he should try to make the correct estimation. On that basis, he should complete the prayer, then after salam, perform two prostrations of forgetfulness.