Sayyiduna Abu Sa'id al-Khudri (may Allah be pleased with him) said that the Messenger of Allah (peace and blessings be upon him) said: "Jibril (peace be upon him) led me in prayer. He prayed Zuhr when the sun had passed its zenith, Asr when the shadow was equal to one stature, Maghrib when the sun had set, Isha when the twilight had disappeared, and Fajr when the true dawn broke. Then on the second day he led me in prayer: he prayed Zuhr when the shadow of everything was equal to it, Asr when the shadow was two statures, Maghrib as soon as the sun set, Isha up to the first third of the night, and Fajr when the sun was about to rise." Then he said: "The time of prayer is between these two times."
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 5424