John Calvin on Leviticus 18:24-25

Leviticus 18:24. Defile not yourselves in any of these things. An old proverb See vol. 2, p. 281, and note. says, that good laws have sprung from evil habits; and God reminds us that for this reason He has been induced expressly to advert to these disgusting and wicked things; for the monstrosities which He mentions would have been concealed in eternal silence had not necessity compelled Him to bring them to light. But since the Canaanitish nations had advanced to such a pitch of licentiousness, that the prodigious sins, which else would have been better concealed, had been but too familiarly known from their wicked habits, God warns His people to beware of their fatal examples. First, when He says that these abominations prevailed amongst the Gentiles, He indicates that evil habits by no means avail as an excuse; nay, that public consent is in vain alleged in defense of vice. But the better to deter them from imitating them, He sets before their eyes the vengeance He is about to take. It is true, indeed, that the nations of Canaan were destroyed for other reasons, but it is not without cause that He sets forth this amongst the rest, for undoubtedly God was offended by such pollutions.