Musnad Ahmad 788:247

Abu Nu‘aym narrated to us, he said: Badr ibn ‘Uthman, the freed slave of the family of ‘Uthman, narrated to us, he said: Abu Bakr ibn Abi Musa narrated to me, from his father, from the Messenger of Allah (peace and blessings of Allah be upon him), that he said: "A questioner came to him asking him about the times of prayer, and he did not answer him anything. Then he commanded Bilal, so he performed the iqamah for the dawn (Fajr) prayer when the dawn broke, while people could hardly recognize one another. Then he commanded him, so he performed the iqamah for the noon (Dhuhr) prayer when the sun had passed the meridian, and the speaker was saying: 'The day has reached its midpoint, or it has not,' and he (the Prophet) was more knowledgeable than them. Then he commanded him, so he performed the iqamah for the afternoon (Asr) prayer while the sun was high. Then he commanded him, so he performed the iqamah for the sunset (Maghrib) prayer when the sun had set. Then he commanded him, so he performed the iqamah for the night (Isha) prayer when the twilight had disappeared. Then, on the following day, he delayed the dawn prayer until he finished it, and the speaker was saying: 'The sun has risen, or it is about to.' He delayed the noon prayer until it was close to the time of the afternoon prayer of the previous day. Then he delayed the afternoon prayer until he finished it, and the speaker was saying: 'The sun has turned red.' Then he delayed the sunset prayer until it was at the disappearance of the twilight. And he delayed the night prayer until it was the first third of the night. Then he called the questioner and said: 'The time is between these two.'"