Verse 4. - Thy seed will I establish forever (see 2 Samuel 7:12, 13; Psalm 130:12). And build up thy throne to all generations. The promises to David were not fulfilled in the letter. After Zerubbabel, no prince of the Davidic house sat on the throne of David, or had temporal sway over Israel. The descendants of David sank into obscurity, and so remained for five centuries. Still, however, God's faithfulness was sure. In Jesus Christ, of the seed of David, the true King of the everlasting kingdom was raised up - every pledge made to David was fulfilled. "Messiah the Prince," eternal King of an eternal kingdom, appeared as the true "Seed' intended, and began his spiritual reign over the spiritual Israel, which still continues, and will continue forever.

89:1-4 Though our expectations may be disappointed, yet God's promises are established in the heavens, in his eternal counsels; they are out of the reach of opposers in hell and earth. And faith in the boundless mercy and everlasting truth of God, may bring comfort even in the deepest trials.Thy seed will I establish for ever,.... Meaning not the natural seed of David, at least not only them; whose family was indeed preserved, though in very low circumstances, until the Messiah came, who sprung from thence, Luke 1:27, but the spiritual seed of Christ, to whom it was promised that he should have a seed, and should see and enjoy it, and which should endure for ever; see Psalm 89:29, and so he always has had a seed to serve him in all generations, in the worst of times, and will; and who are established in him, and will be kept and preserved by him, and whom he will present to his Father, saying, "Lo, I and the children whom thou hast given me", Hebrews 2:13.

and build up thy throne to all generations; and this shows that the passage is not to be understood literally of David, and of his temporal throne and kingdom, which did not last many generations; but of the spiritual throne and kingdom of the Messiah, who sprung from him, called the throne of his father David, whose throne is for ever and ever, and whose kingdom is an everlasting kingdom, Luke 1:32, Psalm 45:6, his throne is in the heavens, where he will reign until all enemies are put under his feet; and it is also in the midst of his church, and in the hearts of his people, where he reigns as King of saints; and he is on the same throne with his Father; it is the same with his, as to glory, power, and authority; on this he will sit, and judge the world at the last day; and on it he will reign with his people a thousand years, in the New Jerusalem state, and after that to all eternity, Revelation 3:21.

Selah. See Gill on Psalm 3:2.