Read Psalm 21.
If Psalm 20 was sung before the king headed out into battle, then Psalm 21 is the victory song that would be sung when he returned: “The king rejoices in your strength, LORD. How great is his joy in the victories you give!” (v. 1).
Like many of the royal psalms, Psalm 21 can’t help but look forward to the day when Jesus will sit on David’s throne. Of course, no king in Israel reigned “for ever and ever” (v. 4). No king received “unending blessings” (v. 6), at least not in this life.
There is probably an element of simple hyperbole here, the sort of thing that happens when ordinary people speak to royalty. For example, when King Darius discovered David had been saved from the lion’s den, David shouted up to him, “O king, live forever!” (Daniel 6:21). It was a nice thing to say in the moment, but neither Daniel nor Darius himself expected the life of any earthly king to last forever.
So, in one sense, these elements in Psalm 21 can be chalked up to mere exaggeration. The king will not live forever, but he will enjoy a long life. His blessings won’t be without end, but they will be great. If David’s royal line were any other dynasty, we might just leave it there, but David had received a promise from God: “When your days are over and you rest with your ancestors, I will raise up your offspring to succeed you, your own flesh and blood, and I will establish his kingdom” (2 Samuel 7:12).
This future king will be God’s Son (v.14), and God’s love will never leave Him (v. 15). He will build a house for God, and His kingdom and His throne will be established forever (vv. 13, 16). As in Psalm 21, there are elements here that can, and do, apply to an earthly king, specifically David’s son Solomon. But the New Testament writers apply this promise to Jesus (see Matthew 19:28–29; Mark 14:58; Luke 1:32; Hebrews 1:5). The author of Hebrews even sees how Jesus fulfilled that bit about punishment in verse 14; see Hebrews 5:8–9.
As if that weren’t enough, the New Testament writers keep going. Jesus’ disciples—you and me included—are going to reign with Him (2 Timothy 2:12). We have become a nation of priest-kings (1 Peter 2:9). The King of kings shares His inheritance with His adopted brothers and sisters. These promises that extended through David to the Messiah, here in Psalm 21, graciously apply to believers who endure till the end!
Eternal life is ours in Christ (John 3:16). Blessings beyond measure are our heavenly inheritance. The apostle Paul put it this way: “And God raised us up with Christ and seated us with him in the heavenly realms in Christ Jesus, in order that in the coming ages he might show the incomparable riches of his grace, expressed in his kindness to us in Christ Jesus” (Ephesians 2:6–7). This is the victory we have in Jesus, ours by the grace of God, through faith in His Son (vv. 8–9).
“Be exalted in your strength, LORD; we will sing and praise your might” (Psalm 21:13).