Musnad Abu Ya'la al-Mawsili 246:20

Zuhayr narrated to us, Affan narrated to us, Hammad ibn Salamah narrated to us, and he said: Amr ibn Dinar informed us, from Nafi ibn Jubayr, from his father, that the Messenger of Allah (may Allah bless him and grant him peace) was on a journey. He said, "Who will watch over us tonight so that we do not sleep through the dawn prayer?" Bilal said, "I will." So he faced the rising of the sun, and sleep overcame them. Nothing awakened them except the heat of the sun. They stood up and hurried, then performed ablution. Bilal gave the call to prayer, and they prayed the two units (Sunnah), then they prayed the dawn prayer.