The title of Psalm 89 names Ethan, the Ezrahite, as its writer, and the psalm closes Book III of the Psalter. Its first half is a hymn. I will sing of the loving kindness of Yahweh forever. Ethan praises God's faithfulness in the heavens and his power over the sea. You have broken Rahab in pieces, a poetic name for the forces of chaos. Righteousness and justice are the foundation of your throne. Loving kindness and truth go before your face.
The second section retells the covenant with David from 2 Samuel 7. God promises, I will establish your offspring forever. Even if his children forsake my law, God says, I will not break my covenant, nor alter what my lips have uttered. Once I have sworn by my holiness, I will not lie to David. His throne would endure like the sun and the moon, the faithful witness in the sky.
The final section is a lament that seems to contradict everything before it. You have renounced the covenant of your servant. You have defiled his crown in the dust. The king's line has been humbled, perhaps at the exile. Ethan asks, Lord, where are your former loving kindnesses? The tension is left open, yet the book closes with a doxology. Christians see the answer in Jesus, the Son of David, whose kingdom has no end (Luke 1:32-33).