Musnad Abu Ya'la al-Mawsili 3:308

Al-Qawariri narrated to us, Kathir bin Hisham narrated to us, Al-Furat bin Salman narrated to us, from Abd al-Karim, from Mujahid, from Abd al-Rahman bin Abi Layla, from Ali bin Abi Talib, who said: The Messenger of Allah (peace and blessings of Allah be upon him) sent me to the butcher who slaughters his sacrificial animals. He commanded me to give away their meat, their hides, and their coverings as charity, and not to give anything of that [the meat or parts of the animal] to him [the butcher] as payment. He said: "We shall give him [the butcher] from other than that."