Question:God condemns bestiality in Leviticus 18:23, but why does He command that the animal be put to death in Exodus 22:19.
Unlike animals, man is given a spirit in the likeness of God (Genesis 1:26-27). In part, this gives man the ability to operate contrary to instinct. We have the ability to choose whether or not to do something. "And if it seems evil to you to serve the LORD, choose for yourselves this day whom you will serve, whether the gods which your fathers served that were on the other side of the River, or the gods of the Amorites, in whose land you dwell. But as for me and my house, we will serve the LORD" (Joshua 24:15). Given the same situation we might chose differently each time we face that situation. Therefore man bears the responsibility when he commits a sin. "The soul who sins shall die. The son shall not bear the guilt of the father, nor the father bear the guilt of the son. The righteousness of the righteous shall be upon himself, and the wickedness of the wicked shall be upon himself" (Ezekiel 18:20).
An animal, however, acts in the boundaries of instinct. Given the same situation, an animal will respond in a similar fashion. Yet, an animal can be trained. This is the reason why an animal is put to death when it kills a human. "Surely for your lifeblood I will demand a reckoning; from the hand of every beast I will require it, and from the hand of man. From the hand of every man's brother I will require the life of man" (Genesis 9:5). Instinct teaches animals to fear men. "And the fear of you and the dread of you shall be on every beast of the earth, on every bird of the air, on all that move on the earth, and on all the fish of the sea. They are given into your hand" (Genesis 9:2). But an animal who breaks that instinctive fear is a danger to people. And this is true even though an animal is not put to death for killing another animal. Animals do not have spirits, so they are treated with kindness but not as equals to humans.
An animal who engages in acts of sex with a human has been trained to break its instinctive actions. An animal normally will only mate with a member of its own species. Now that it has been trained, it will continue to act contrary to nature. Thus the animal is put to death along with the human who trained. it. "If a man mates with an animal, he shall surely be put to death, and you shall kill the animal. If a woman approaches any animal and mates with it, you shall kill the woman and the animal. They shall surely be put to death. Their blood is upon them" (Leviticus 20:15-16).