Sayyiduna Ibn Abbas (may Allah be pleased with them both) says that the Messenger of Allah (peace and blessings be upon him) said: "Whomever you see committing bestiality with an animal, kill them both, the animal too." It was asked: What is the animal's fault? He said: I did not hear anything about this from the Prophet (peace and blessings be upon him), but my opinion is that benefiting from that animal, or eating its meat, is now disliked.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحدود / 17035