Sahih Bukhari Volume 4, Book 54, Hadith Number 444.

Narated By Ibn Shihab : Once Umar bin Abdul Aziz delayed the ‘Asr prayer a little. ‘Urwa said to him, “Gabriel descended and led the prayer in front of the Prophet ” On that ‘Umar said, “O Urwa! Be sure of what you say.” “Urwa, “I heard Bashir bin Abi Masud narrating from Ibn Masud who heard Allah’s Apostle saying, ‘Gabriel descended and led me in prayer; and then prayed with him again, and then prayed with him again, and then prayed with him again, and then prayed with him again, counting with his fingers five prayers.”