Albert Barnes Commentary Psalms 89:29

"His seed also will I make to endure for ever, And his throne as the days of heaven." — Psalms 89:29 (ASV)

His seed also will I make to endure for ever – that is, His posterity will occupy the throne:

1. This would have been true of His descendants, if they had been faithful to God and had not revolted from Him.

2. It is true of Him who is the successor of David in His spiritual kingdom, the Lord Jesus, the Messiah. (Compare the notes at Isaiah 9:6-7).

And his throne as the days of heaven – as long as the heavens endure; that is, to the end of the world. (Compare the notes on Psalm 72:5, Psalms 72:7, and Psalm 72:17).