Abu Dawud Book 33, Hadith Number 4449.

Narated By Abdullah ibn Abbas : The Prophet (PBUH) said: If anyone has sexual intercourse with an animal, kill him and kill it along with him. I (Ikrimah) said: I asked him (Ibn Abbas): What offence can be attributed to the animal/ He replied: I think he (the Prophet) disapproved of its flesh being eaten when such a thing had been done to it.