Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) narrates: We were with the Messenger of Allah (peace and blessings be upon him) on a journey, and the people said: "Let us halt for the night." He (peace and blessings be upon him) said: "Who will wake us?" I said: "I will keep watch and wake you all." Then I fell asleep and they slept too, and we did not wake until the heat of the sun was upon our heads. The Messenger of Allah (peace and blessings be upon him) was the last of us to wake; he (peace and blessings be upon him) and the people stood up and performed ablution, then he (peace and blessings be upon him) led two rak'ahs, and then he prayed the Fajr prayer.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 10311