The Book of Prayers (Kitab Al-Salat)
Muslim :: Book 4 : Hadith 1268
Ibn Shibab reported: 'Umar b. 'Abd al-'Aziz deferred the afternoon prayer somewhat and 'Urwa said to him: Gabriel came down and he led the Messenger of Allah (may peace be upon him) in prayer. 'Umar said to him: O 'Urwa, are you aware of what you are saying? Upon this he ('Urwa) said: I heard Bashir b. Abu Mas'ud say that he heard Abu Mas'ud say that he heard the Messenger of Allah (may peace be upon him) say: Gabriel came down and acted as my Imam, then I prayed with him, then I prayed with him, then I prayed with him. then I prayed with him. then I prayed with him. reckoning with his fingers five times of prayer.