Musnad Ahmad 5:756

Mu'adh narrated to us, Zuhayr ibn Mu'awiyah Abu Khaythamah informed us, from 'Abd al-Karim al-Jazari, from Mujahid, from 'Abd al-Rahman ibn Abi Layla, from 'Ali, may Allah be pleased with him, who said: "The Messenger of Allah, peace and blessings of Allah be upon him, commanded me to oversee his sacrificial animals, and to give away their meat, their skins, and their coverings in charity, and not to give the butcher anything from them." He said: "We give him [the butcher] from our own [possessions]."