His throne as the sun before me In respect of perpetual duration, as appears, both from the foregoing and following words. It shall be established as the moon As the moon, though subject to eclipses, and frequent and manifold changes, yet doth constantly and perpetually remain in heaven, as a witness of my covenant of the night, as it is called Jeremiah 33:20, so shall the house and kingdom of David continue for ever. And as a faithful witness in heaven By which may be meant either, 1st, The moon last mentioned, which was to be a faithful witness to this promise of God so long as it continued in the heavens; or the rainbow, which, though in itself it be unstable and transient, and doth but seldom appear, yet in Scripture is mentioned as God's faithful and perpetual witness, being called a token of God's everlasting covenant, between him and every living creature for perpetual generations, Genesis 9:12-16.
Related Commentaries of Psalms 89:36
Psalms 89:36-37
36 His seed shall endure for ever, and his throne as the sun before me.
37 It shall be established for ever as the moon, and as a faithful witness in heaven. Selah.