Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him) led us in prayer, and there was either a deficiency or an addition in it. Ibrahim says: This doubt occurred to Alqamah, or Alqamah narrated it from Abdullah bin Mas'ud. After completing the prayer, the Messenger of Allah (peace and blessings be upon him) turned towards us, so we asked: O Messenger of Allah! Has a new command regarding prayer been revealed? He said: What happened? We informed him, so he folded his legs and, facing the Qiblah, performed two prostrations. Then, turning his blessed face towards us, he said: If a new command regarding prayer had been revealed, I would have informed you, but I am also a human being; I remember as you do, and I forget as you do. When I forget, remind me. Whoever has doubt in his prayer should determine what is more correct, then complete the prayer accordingly, and after saying salam, perform two prostrations.