What does Proverbs 24:9 mean?

The Hebrew word zimmat' here refers to "devising:" when someone invents or plots. In this context, it means those who scheme about evil (Proverbs 24:8). "Folly" is often mentioned in the book of Proverbs as a state of rejecting or ignoring God's wisdom (Proverbs 5:23; 19:3; 27:22) and is what defines the "fool." The prior verse pointed out that those who produce evil plots suffer a negative reputation: others will openly call them "schemers" (Proverbs 24:8). The statement in this verse completes the thought. Planning immorality, plotting to do evil, inventing ways to sin, or imagining wicked actions are all sins in and of themselves. This wisdom foreshadows Jesus' teaching that sin begins in the heart and mind (Matthew 5:21–22). Even if no actions are taken, the schemes and fantasies are already offensive to God (Matthew 5:27–28). Some believe thoughts are not sinful unless they are acted on, but Scripture disagrees.

Similarly, "scoffers" are those who mock or laugh—they "sneer" at wisdom instead of accepting it (Proverbs 1:22; 9:12; 14:6; 19:28). "Abomination" comes from a term meaning something "disgusting" or "repulsive" (Proverbs 6:16; 15:9; 21:27). Not only are those who plan evil offensive to God, but other men also detest them. The prior verse also mentioned this idea, noting that evil schemers will be labeled and condemned by others (Proverbs 24:8). Jude 1:18–19 predicts that this attitude will become common as the world continues to drift away from God.