It is narrated from Sayyiduna Abu Sa'id al-Khudri (may Allah be pleased with him) that one day the Messenger of Allah (peace and blessings be upon him) addressed us and recited Surah Sad. When he reached the (verse of) prostration, he (peace and blessings be upon him) came down and prostrated, and we also prostrated with him. Then he recited it once again, and when he reached the (verse of) prostration, we got ready to prostrate. When he (peace and blessings be upon him) saw us (ready), he said: "This is only the repentance of a Prophet, but I see that you have got ready to prostrate." So he (peace and blessings be upon him) came down and prostrated, and we also prostrated. This hadith is sahih (authentic) on the condition of the two Shaykhs, but they did not record it, while the prostration of Surah Sad has been recorded by Imam Bukhari. The purpose of bringing it here in the Book of Friday is that when the imam recites a verse of prostration on the pulpit on Friday, the sunnah is that he comes down and prostrates.