Musnad Abu Ya'la al-Mawsili 151:44

Abu Bakr narrated to us, Husayn bin Ali narrated to us, from Za'idah, from Simak, from al-Qasim bin Abd al-Rahman, from his father, from Abdullah, who said: We traveled by night one night with the Messenger of Allah (may Allah bless him and grant him peace), and we said: "O Messenger of Allah, if only we touched the ground and slept, and our mounts grazed." He said: "Then who will guard us?" I said: "I will." Then my eyes overcame me, and nothing awakened us except that the sun had risen. The Messenger of Allah (may Allah bless him and grant him peace) did not awaken except by our talking. He said: So he ordered Bilal, and he gave the Adhan, then he stood and prayed with us.