John Gill Commentary Leviticus 18:24

"Defile not ye yourselves in any of these things: for in all these the nations are defiled which I cast out from before you;" — Leviticus 18:24 (ASV)

Defile not you yourselves in any of these things In incestuous copulations and marriages, in adultery, corporeal and spiritual, and bestiality:

for in all these the nations are defiled which I cast out before you ; that is, the seven nations of the land of Canaan, which God was about to eject out of their land to make room for the Israelites, and that on account of the above shocking vices which abounded among them; so that in some sense the land they dwelt upon was defiled by them, and called for vengeance on them, as even loathing its inhabitants, as afterwards suggested.