Sahih Muslim Book 7, Hadith Number 3022.

Chapter : One should offer as sadaqa the meat and hide of the sacrificial animal.

Ali b. Abi Talib (Allah be pleased with him) reported: Allah’s Apostle (may peace be upon him) put him in charge of his sacrificial animals, and commanded him to distribute the whole of their meat, hides, and saddle cloths to the poor, and not to give to the butcher anything out of them.