What does Psalm 5:10 mean?

In this verse David appeals to God to execute vengeance on his enemies (Psalm 3:1). He describes them as guilty of abundant transgressions—violations of God's laws—and also guilty of rebelling against God. The enemies in question are rebels being led by David's own son, Absalom (2 Samuel 15:13–14). Even so, David does not say they are guilty of rebelling against him; he indicates they are mutinying against God. David was appointed by God to be king of Israel, so by trying to overthrow King David, the enemy was in fact rebelling against God.

David was correct to view sinning as defiance of God. In his prayer of confession after committing adultery with Bathsheba and arranging the death of her husband, David prayed, "Against you, you only, have I sinned and done what is evil in your sight" (Psalm 51:4). Undoubtedly, we would sin less often if we viewed every sin as an assault on God. Indeed, our sins caused Jesus to die on the cross. First Corinthians 15:3 says that Christ died for our sins.