For what reason must the animal involved in bestiality be killed?

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There are differing explanations for the cause necessitating the animal's death. One reason is to prevent the perpetrator from being mocked and his crime being remembered by seeing the animal. This is supported by a narration from Ibn Battah, where the Prophet, peace be upon him, said: "Whoever you find committing bestiality, kill him, and kill the animal. They asked: O Messenger of Allah, what is wrong with the animal? He replied: So that one does not say, 'This one and this one.'" Another reason suggested is to prevent the birth of deformed offspring. A third reason cited is to prevent the animal from being eaten, which is what Ibn Abbas alluded to in his reasoning.