Al-Muwatta Hadith 15.16

Yahya related to me from Malik from Hisham ibn Urwa from his father that Umar ibn al-Khattab once recited a piece of Qur'an requiring a prostration while he was on the mimbar on the day of jumua, and he came down and prostrated, and everyone prostrated with him. Then he recited it again the next jumua and everybody prepared to prostrate but he said, "At your ease. Allah has not prescribed it for us, unless we wish." He did not prostrate, and he stopped them from prostrating. Malik said, "The imam does not come down and prostrate when he recites a piece of Qur'an requiring a prostration while he is on the mimbar." Malik said, "The position with us is that there are eleven prescribed prostrations in the Qur'an, none of which are in the mufassal." Malik said, "No-one should recite any of the pieces of Qur'an that require a prostration after the prayers of subh and asr. This is because the Messenger of Allah, may Allah bless him and grant him peace, forbade prayer after subh until after the sun had risen, and after asr until the sun had set, and prostration is part of the prayer. So no-one should recite any piece of Qur'an requiring a prostration during these two periods of time." Malik was asked whether a menstruating woman could prostrate if she heard some-one reciting a passage of Qur'an requiring a prostration, and he said, "Neither a man nor a woman should prostrate unless they are ritually pure." Malik was asked whether a man in the company of a woman who was reciting a passage of Qur'an requiring a prostration should prostrate with her, and he said, "He does not have to prostrate with her. The prostration is only obligatory for people who are with a man who is leading them. He recites the piece and they prostrate with him. Some one who hears a piece of Qur'an that requires a prostration being recited by a man who is not leading him in prayer does not have to do the prostration."