Musnad Ahmad 27:1932

'Abd al-Razzaq narrated to us, Ma'mar informed us, from al-Zuhri, from Salim, who said: Ibn 'Umar was asked about the *mut'ah* of Hajj, so he commanded it and said: "Allah the Exalted made it lawful, and the Messenger of Allah, may Allah bless him and grant him peace, commanded it." Al-Zuhri said: And Salim informed me that Ibn 'Umar said: "The 'Umrah during the months of Hajj is complete and fulfilled; the Messenger of Allah, may Allah bless him and grant him peace, acted upon it, and the Book of Allah the Exalted was revealed concerning it."