Al-Muwatta Hadith 1.25

Yahya related to me from Malik from Ibn Shihab from Said ibn al-Musayyab that the Messenger of Allah, may Allah bless him and grant him peace, travelled by night on the way back from Khaybar.Towards the end of the night he stopped for a rest and told Bilal to stay awake to keep watch for the subh prayer. The Messenger of Allah, may Allah bless him and grant him peace, and his companions slept. Bilal stayed on guard as long as was decreed for him and then he leant against his riding camel facing the direction of the dawn and sleep overcame him and neither he nor the Messenger of Allah nor any of the party woke up until the sun's rays had struck them. The Messenger of Allah, may Allah bless him and grant him peace, was alarmed. Bilal excused himself, saying, "Messenger of Allah! The One who took your self was the One who took myself. "The Messenger of Allah, may Allah bless him and grant him peace, ordered the party to move on and so they roused thei r mounts and rode on a short distance. The Messenger of Allah, may Allah bless him and grant him peace, ordered Bilal to give the iqama and then led them in the subh prayer. When he had finished he said, "Anyone who forgets a prayer should pray it when he remembers. Allah theBlessed and Exalted says in His book, 'Establish the prayer to remember Me.'"