Sahih Bukhari Volume 005, Book 059, Hadith Number 344.
Hadith Section/Book: Sahih Bukhari Sahih Bukhari Book 59. Military Expeditions Led by the Prophet (PBUH) (Al-Maghaazi)
Narrated By Az-Zuhri: I heard 'Urwa bin Az-Zubair talking to 'Umar bin 'Abdul 'Aziz during the latter's Governorship (at Medina), he said, "Al-Mughira bin Shu'ba delayed the 'Asr prayer when he was the ruler of Al-Kufa. On that, Abu Mas'ud. 'Uqba bin 'Amr Al-Ansari, the grand-father of Zaid bin Hasan, who was one of the Badr warriors, came in and said, (to Al-Mughira), 'You know that Gabriel came down and offered the prayer and Allah's Apostle prayed five prescribed prayers, and Gabriel said (to the Prophet), "I have been ordered to do so (i.e. offer these five prayers at these fixed stated hours of the day)."