What does Psalm chapter 21 mean?

Psalm 21 pairs with Psalm 20, which seems to come before David entered a battle. This song celebrates victory and expresses confidence in future success.

This praise of God begins by expressing the king's victory and his appreciation for God's favor. Verse 4 makes a reference to "length of days forever and ever," which seems to be a reference to the Messiah. In 2 Samuel 7:11–16, the Lord promises to establish David's descendant(s) on the throne for all time. It was these guarantees from God, and the success he obtained, that made David and his people confident in God's goodness and faithfulness (Psalm 21:1–7).

The second half of the psalm anticipates future victories for king David. These are credited to God, as the one who "swallows up" enemies of His chosen people. As part of this celebration, Scripture reminds us that following in the sinful footsteps of our ancestors is no excuse. Those who continue the sins of their parents can expect to face God's judgment. This passage also uses a vivid illustration of how David's enemies will flee him. They will respond as drastically as would someone having a drawn bow pointed directly into their face. This is the depth of faith the people express in God's power and plans (Psalm 21:8–13).