Sayyiduna Anas (may Allah be pleased with him) says: When the Messenger of Allah (peace and blessings be upon him) conquered Khaybar, we came upon donkeys outside the town, which we slaughtered and began to cook. Then the caller of the Messenger of Allah (peace and blessings be upon him) announced: "Allah and His Messenger (peace and blessings be upon him) forbid you from eating the meat of donkeys, for it is filth from the work of Satan." So the pots, boiling with the meat, were overturned.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الضحايا / 19466