Commentaries
18:1-30 Unlawful marriages and fleshly lusts. - Here is a law against all conformity to the corrupt usages of the heathen. Also laws against incest, against brutal lusts, and barbarous idolatries; and the enforcement of these laws from the ruin of the Canaanites. God here gives moral precepts. Close and constant adherence to God's ordinances is the most effectual preservative from gross sin. The grace of God only will secure us; that grace is to be expected only in the use of the means of grace. Nor does He ever leave any to their hearts' lusts, till they have left him and his services.
30. Therefore shall ye keep mine ordinance, that ye commit not any one of these abominable customs—In giving the Israelites these particular institutions, God was only re-delivering the law imprinted on the natural heart of man; for there is every reason to believe that the incestuous alliances and unnatural crimes prohibited in this chapter were forbidden to all men by a law expressed or understood from the beginning of the world, or at least from the era of the flood, since God threatens to condemn and punish, in a manner so sternly severe, these atrocities in the practice of the Canaanites and their neighbors, who were not subject to the laws of the Hebrew nation.