It is narrated from Sayyiduna Abdullah bin Amr (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) was asked about the time of prayer, and he (peace and blessings be upon him) said: "The time of the Fajr prayer lasts as long as the first edge of the sun has not risen; the time of the Zuhr prayer is when the sun has declined from the middle of the sky, as long as the time of Asr has not come; the time of the Asr prayer is as long as the sun has not turned yellow and its first edge has not set; the time of the Maghrib prayer is when the sun has set, as long as the redness of twilight has not ended; and the time of the Isha prayer is until half the night."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 1706