Sahih Bukhari Volume 001, Book 010, Hadith Number 500.
Narated By Ibn Shihab : Once'Umar bin 'Abdul 'Aziz delayed the prayer and 'Urwa bin Az-Zubair went to him and said, "Once in 'Iraq, Al-MughTra bin Shu'ba delayed his prayers and Abi Mas'ud Al-Ansari went to him and said, 'O Mughira! What is this? Don't you know that once Gabriel came and offered the prayer (Fajr prayer) and Allah's Apostle prayed too, then he prayed again (Zuhr prayer) and so did Allah's Apostle and again he prayed ('Asr prayers and Allah's Apostle did the same; again he prayed (Maghrib-prayer) and so did Allah's Apostle and again prayed ('Isha prayer) and so did Allah's Apostle and (Gabriel) said, 'I was ordered to do so (to demonstrate the prayers prescribed to you)?'" 'Umar (bin 'Abdul 'AzTz) said to 'Urwa, "Be sure of what you Say. Did Gabriel lead Allah's Apostle at the stated times of the prayers?" 'Urwa replied, "Bashir bin Abi Mas'ud narrated like this on the authority of his father." Urwa added, "'Aisha told me that Allah's Apostle used to pray 'Asr prayer when the sun-shine was still inside her residence (during the early time of 'Asr)."