Musnad Ahmad 5:32

Sufyan narrated to us, from Abd al-Karim, from Mujahid, from Ibn Abi Layla, from Ali, who said: The Messenger of Allah (peace and blessings of Allah be upon him) commanded me to distribute his sacrificial animals (budn) and to oversee them, and to distribute their skins and their coverings. He commanded me not to give the butcher anything from them, and he said: "We shall give him from what we have."