Sayyiduna Abu Sa'id Khudri (may Allah be pleased with him) said: One day the Messenger of Allah (peace and blessings be upon him) delivered a sermon and recited Surah Sad, and when he reached the verse of prostration, he came down from the pulpit and performed prostration, so we also performed prostration with him. Then, on another occasion, during the (Friday sermon), he recited Surah Sad again, so we prepared ourselves for prostration. When the Messenger of Allah (peace and blessings be upon him) saw us in this state, he said: "This is the mention of a prophet's repentance (i.e., prostration is not obligatory), but I have seen you preparing for prostration." So the Messenger of Allah (peace and blessings be upon him) came down and performed prostration, and we also performed prostration with him.