Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) narrates: The Prophet Muhammad (peace and blessings be upon him) once added something to the prayer while leading us, or perhaps omitted something. It was submitted to him, "O Messenger of Allah (peace be upon him), has a new command regarding the prayer come?" The Prophet (peace be upon him) said: "If a new command had come, I would have informed you about it. But I am also a human being; I forget just as you forget. If any one of you is uncertain about his prayer, then he should consider which option is closer to being correct, and then complete his prayer on that basis, and then perform two prostrations of forgetfulness (sujood as-sahw)." (Imam Ibn Hibban, may Allah have mercy on him, says:) The narrator named Ibrahim bin Mughira is the son-in-law of Abdullah bin Mubarak. And he is trustworthy.