Muhammad bin Sirin (may Allah have mercy on him) narrates from Sayyiduna Anas (may Allah be pleased with him) that three men came to the Prophet (peace and blessings be upon him), one after another, and said that the donkeys would be finished off by being eaten. So he (peace and blessings be upon him) had it announced: "Allah and His Messenger forbid you from eating the meat of domestic donkeys, for it is impure." Then the pots were overturned while they were boiling.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الضحايا / 19465