This chapter continues the themes of the previous two. Here we also read of the punishments applicable to various transgressions, v5, 13. God's standards must be applied by His people.
v1-5: Idolatry is serious, and demands punishment. There was a responsibility upon the Israelites to punish the wrong-doer. Since sin can spread, it must be dealt with promptly and decisively. Where the people turn a blind eye (v4), that is to condone or tolerate the wrong, and is also punishable.
v6: Spiritism and occult practices are consistently condemned in Scripture. Gentile nations commonly practised such things. 19.31 states that such things defile the people. This verse states that the Lord will cut off from His people any who practise spiritism. Thus, in v7, the people are instructed to sanctify themselves, including ridding themselves of such evil. In v26, we are reminded that the Lord called His people to be distinct from other nations. In v27, the guilty man had to be stoned to death.
We note that prohibitions against spiritism are linked with teaching about holiness. This is no surprise, as the God who is perfectly holy demands holiness from His people.
v7-8: Holiness is from God's work and our commitment. (See also v26). Holiness must be the shared desire of God's people.
v9-21: A series of instructions, followed by punishments for those who disobey. The reason is found in v14, "so that no wickedness will be among you", quoted in 1 Cor 5.13.
v9: See also 19.3. Failure to honour parents was serious. It is not insignificant that disobedience to parents is a mark of general godlessness (Rom 1.30; 2 Tim 3.2).
v10: Adultery, of which King David was guilty. Such is the grace of God that He put away David's sin. We see that Jesus Christ, the Son of God, bore this sin, and was put to death instead.
v11-12: In a similar vein, sexual contact with a close relative is punished. It is "perversion."
v13: Homosexual practices are condemned; see 18.22. Note that this is not presented as being much worse than adultery, nor idolatry. There can be a tendency for certain sins to be thought of as more serious; the additional word here is "detestable", i.e: disgusting. There is forgiveness in Christ (1 Cor 6.9-11).
v14-16: More sexual wickedness; again, we must consider that the Canaanite nations were guilty of such things (see v23).
v17-21: Some sins were not punishable by death. God is fair and reasonable in His dealing with mankind. And some sins are manifestly more serious than others.
v22-24: See also 18.24-25. The Canaanite peoples were guilty of all these wrong practices, particularly sexual perversions (referred to in most verses, v9-21). As a result, the land vomited them out. Individuals, such as Rahab, who turned from such things, could be delivered and saved. What was important was that the people of God did not follow such practises.
The land was the inheritance promised by God, and therefore there has to be an on going testimony of true holiness.
v25-26: The principle of separation, applied to the eating of animals, as well as to sexual relations, worship, and other matters.
v27: Evidently, spiritism was widespread in Canaan, and so an extra prohibition was added here. Spiritism did not and could not promote holiness in life.