Set — Establish his power and dominion. The sea — The mid — land sea. The rivers — Euphrates, called rivers, in regard of divers branches of it, and rivers which flow into it. So here is a description of the uttermost bounds of the promised land.
Related Commentaries of Psalms 89:25
Psalms 89:25
25 I will set his hand also in the sea, and his right hand in the rivers.