Musnad Ahmad 20:18

Waki’ narrated to us, Mis’ar narrated to us, from a sheikh from [the tribe of] Fahm, who said: I heard Abdullah ibn Ja’far say: Meat was brought to the Messenger of Allah, may Allah bless him and grant him peace, and the people began to throw the meat to him. The Messenger of Allah, may Allah bless him and grant him peace, said: "Indeed, the best of meat is the meat of the back."