Sayyiduna Ibn Abbas (may Allah be pleased with them both) narrated from the Messenger of Allah (peace and blessings be upon him), he (peace be upon him) said: "If you see anyone committing an evil act (a lustful act) with an animal, then kill that person and the animal. And if you see anyone committing the act of the people of Lot, then kill both the one who does it and the one to whom it is done (the active and the passive participant)."