Musnad Ahmad 32:146

Sufyan ibn 'Uyaynah narrated to us, from Ayyub, from Muhammad, from Anas, who said: The Prophet, peace and blessings of Allah be upon him, arrived at Khaybar in the morning, and they had come out with their shovels. When they saw him, they said: "Muhammad and the army, Muhammad and the army," then they turned and ran toward the fortress. The Messenger of Allah, peace and blessings of Allah be upon him, raised his hands, then said "Allahu Akbar" three times, then said: "Khaybar is ruined. Indeed, when we descend into the courtyard of a people, evil is the morning of those who were warned." We captured donkeys outside the village and cooked them. Then the Messenger of Allah, peace and blessings of Allah be upon him, said: "Indeed, Allah the Almighty and His Messenger forbid you from domestic donkeys, for they are an abomination from the work of Satan." Sufyan said: "Muhammad and the army" means: and the military force.