Musnad Ahmad 455:5

Bahz narrated to us, he said: Hammad bin Salamah narrated to us, Ya’la bin ‘Ata’ narrated to us, from Yazid bin Talq, from ‘Abd al-Rahman bin al-Baylamani, from ‘Amr bin ‘Abasah, who said: I came to the Messenger of Allah, peace and blessings of Allah be upon him, and said: "O Messenger of Allah, who has accepted Islam with you?" He said: "A free man and a slave," meaning Abu Bakr and Bilal. I said: "O Messenger of Allah, teach me from what Allah has taught you and I am ignorant of. Is there any hour better than another?" He said: "The last part of the middle of the night is the best, for it is witnessed and accepted until you pray the dawn (Fajr). Then refrain until the sun rises, as long as it is like a shield, until it spreads, for it rises between the two horns of a devil, and the disbelievers prostrate to it. Then pray, for it is witnessed and accepted until the spear (shadow) is level with its shadow. Then refrain, for it is an hour in which Hell is stoked. Then when it passes the meridian, pray, for it is witnessed and accepted until you pray the afternoon (Asr). Then refrain until the sun sets, for it sets between the two horns of a devil, and the disbelievers prostrate to it." And ‘Amr bin ‘Abasah used to say: "I am one-fourth of Islam." And ‘Abd al-Rahman used to pray two rak'ahs after the afternoon (Asr) prayer.