Leviticus 18:1

And the LORD spake unto Moses, saying,

The verse records the Lord speaking to Moses to introduce the instruction and laws that follow in the chapter. It stands in Leviticus 16 to 18, where God's commands are repeated often and given in minute detail, showing that God is particular about details. It opens part of a block from chapters 17 to 24 made up of various laws, ordinances, prohibitions, and precepts, the reason for most of which is self-evident. It opens God's command to the children of Israel not to do after the doings of the land of Egypt and the land of Canaan, prefacing the list of prohibited sins beginning in Leviticus 18:6 and closing in Leviticus 20:22-26.

The verse introduces explicit laws against marriage and sexual relations between close relatives, defining the prohibited degrees of kinship and including prohibitions against incest and other sexual abominations. Marriage between cousins is not among the prohibited degrees of kinship in Leviticus 18, so no Scripture forbids cousins marrying. These laws express a moral standard binding on all nations and not merely Jewish ritual rules or pollutions, since the chapter calls such acts abominations for which the Canaanites and earlier inhabitants were driven out and the land is said to have vomited them out, showing they were offenses judged by God.

The Egyptians and Canaanites were Gentiles who were cast out and abhorred solely because they did all these forbidden things, which include violations of every command of the Decalogue. This proves the Ten-Commandment law was binding on all men before it was spoken from Sinai and was known wherever conscience was not seared by persistent disobedience, and not being local or for a special people then, it is still binding now and is used by the Spirit in convincing the world of sin. The prohibitions concerning incest and marriages violating degrees of kinship help explain why bastard in Deuteronomy 23:2 may mean the offspring of such unions rather than every child born out of wedlock.

The chapter exposes the evil associated with the nations that lived in Canaan, including the abominable practices associated with sun-worship, as evil influences God's people were to shun. The chapter is a warning about the destructive possibilities of spiritualism and resistance to God's truth. The chapter that follows connects to sexual vice and immorality practiced in cities and to the sins that brought destruction on the world in Noah's day.