Albert Barnes Commentary Psalms 89:36

"His seed shall endure for ever, And his throne as the sun before me." — Psalms 89:36 (ASV)

His seed shall endure forever ... - His posterity. See the notes at (Psalms 89:29). There, the expression is, his throne as the days of heaven. Here it is, his throne as the sun before me. The meaning is the same. It would stand through all time. Compare the notes at (Psalms 72:5).