Musnad Abu Ya'la al-Mawsili 106:75

Muhammad narrated to us, Muhammad ibn Ja'far narrated to us, Shu'bah narrated to us, from Abu Ishaq, who said: Al-Bara' said: We obtained donkeys on the day of Khaybar, so the announcer of the Messenger of Allah (may Allah bless him and grant him peace) called out: "Overturn the cooking pots."