It shall be established for ever as the moon, and as a faithful witness in heaven. Selah. As the moon, and as a faithful witness in heaven - That is, as long as the sun and moon shall endure, as long as time shall last, his kingdom shall last among men. The moon appears to be termed a faithful witness here, because by her particularly time is measured. Her decrease and increase are especially observed by every nation, and by these time is generally estimated, especially among the eastern nations. So many moons is a man old; so many moons since such an event happened; and even their years are reckoned by lunations. This is the case with the Mohammedans to the present day. Or the rainbow may be intended; that sign which God has established in the cloud; that faithful witness of his that the earth shall no more be destroyed by water. As long therefore as the sun, the moon, and the rainbow appear in the heavens, so long shall the spiritual David reign, and his seed prosper and increase.
Selah - It is confirmed; it shall not fail.