Al-Matalib al-'Aliyah 249 — The prayer times

It is narrated from Abu Mijlaz (may Allah have mercy on him) that a man came to the Messenger of Allah (peace and blessings be upon him) and asked him about the times of the prayers. The narrator said: (For the purpose of teaching,) the Messenger of Allah (peace and blessings be upon him) prayed the Fajr prayer (on the first day) in the ghalas, that is, the early darkness of dawn, then he prayed the Asr prayer in daylight (that is, while the sun was still high). When the next day came, he delayed the Fajr prayer until (people) began to say: "What has held him back?" Then he led the prayer. Then he delayed the Asr prayer as well, until it was said: "What has held him back?" Then he led the prayer. After that he asked: "Where is the questioner?" He replied: Here I am. He asked: "Were you present with us yesterday?" He replied: Yes. He asked: "And were you present with us today as well?" He replied: Yes. He said: "Whichever of these (limits) you choose, that is a time for the prayer, and what is between the two is also a time for the prayer."
Musnad al-Harith (Zawa'id al-Haythami): 249. The chain of this report is mursal because Abu Mijlaz is a Successor (Tabi'i); however, there are other authentic hadith on this subject that support it.