Musannaf Ibn Abi Shaybah 3264 — All the prayer times

Nafi' bin Jubayr said: Sayyiduna Umar (may Allah be pleased with him) wrote to Sayyiduna Abu Musa (may Allah be pleased with him) a letter in which was written: "Pray Zuhr when the sun declines; pray Asr while the sun is white and bright. Pray Maghrib when night and day merge into each other. Pray Isha whenever you wish during the night, and pray Fajr when the light has spread."