Psalm 89:4

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 ) ( 2:4 ) ( Acts 13:23 ) , 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 ( Psalms 89:29 Psalms 89:36 ) ( Isaiah 59:21 ) , 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 Luke 1:33 ) ( Psalms 45:6 ) ( Daniel 2:44 ) , 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 ) ( Revelation 20:4 Revelation 20:5 Revelation 20:11 ) ( Revelation 22:3 Revelation 22:4 ) .

Selah. (See Gill on Psalms 3:2).