Musnad Ahmad

Hazrat Mughirah bin Shu’bah (may Allah be pleased with him) reports that once the Prophet Muhammad (peace and blessings be upon him) led us in the Zuhr or Asr prayer. After completing two rak’ahs, he did not sit but stood up. The followers said “Subhan Allah,” but the Prophet (peace and blessings be upon him) stood up and, with a gesture of his hand, instructed us to stand as well. When he finished the prayer, he said salam and performed two prostrations of forgetfulness (sahw). He then said: “If you remember before standing up completely, then sit down. But if you have already stood up completely, then do not sit down.”