Sunan an-Nasa'i — The Book of the Times (of Prayer) — Hadith No: 513
Translation
It was narrated from Jabir bin 'Abdullah that Jibril came to the Prophet (ﷺ) to teach him the times of prayer. Jibril went forward, with the Messenger of Allah (ﷺ) behind him and the people behind the Messenger of Allah (ﷺ), and he prayed Zurh when the sun had passed its zenith. Then he came to him when the shadow of a person was equal to his height, and did as he had done before; Jibril went forward, with the Messenger of Allah (ﷺ) behind him and the people behind the Messenger of Allah (ﷺ), and he prayed 'Asr. Then Jibril came to him when the sun had set; Jibril went forward, with the Messenger of Allah (ﷺ) behind him and the people behind the Messenger of Allah (ﷺ), and he prayed Al-Ghadah. [1] Then he came to him on the second day when a man's shadow was equal to his height, and did as he had done the day before, he prayed Zuhr. Then he came to him when the shadow of a man was twice his height, and did what he had done the day before, and prayed 'Asr. Then he came to him when the sun had set and did what he had done the day before, and prayed Maghrib. Then we slept and got up, and slept and got up again. Then he came to him and did what he had done the day before and prayed 'Isha.' The he came to him when the (the light of) dawn was spread (on the horizon) [2] and the starts were still clear in the sky, and he did the same as he had done the day before, and prayed Al-Ghadah. Then he said:' The time between these two is the time for prayer.'" [1] Meaning Fajr, the morning prayer. [2] The Fajr prayer was elongated because the Prophet recited at length during the prayer, so that it ended just before sunrise. That defined the end of the time for Fajr, as the beginning of the time was defined by the moment when he started the first Rak'ah