The Sin of One Bestiality

Question :

Should a sheep be killed if a person has sex with it?

Answer:

Allah has permitted a man to take pleasure with his wife and with his slave-girl and to have sexual intercourse with them. The exceptions for that, are the situations when He has forbidden him to take pleasure with his wife and his slave-girl. Such as the time of her menstrual period. He has also forbidden him to have sexual intercourse with other than them, and declared it to be a transgression of His Limits; Allah, Most High says:
"And those who guard their chastity (i.e. private parts, from illegal sexual acts) Except from their wives or (the slaves) that their right hands possess, for then, they are free from blame; But whoever seeks beyond that, then those are the transgres- sors:

Accordingly, a man having sex with a sheep or any other such animal is forbidden and a transgression of Allah's Limits. But it does not require the legal punishment to be imposed, as in the case when a man has illegal sexual intercourse with a woman. Rather, it is only necessary for the person to be rebuked as the Judge sees fit.

As for the sheep, it is neither punished nor rebuked, since it is not responsible under the Islamic Law. However, it should be removed far from the place where the crime against it took place, either by selling it, and transferring it to another area, or by slaughtering it. Then hopefully, the crime will be forgotten about and the people will stop talking about it. But this is not considered a punishment or a rebuke, because it is the right of its owner to slaughter it and to sell it without anyone considering it a punishment.

It has been reported from the Prophet that he ordered that a riding beast with which someone had sex be killed. Based upon this, slaughtering it is better, if its meat may be eaten, such as a sheep or the like, in accordance with this Hadith, and in order to stop talk about it.

Source:
The Permanent Committee
Fatawa Islamiyah, Vol. 6 Pages 201-202