John Gill Commentary Psalms 89:25

"I will set his hand also on the sea, And his right hand on the rivers." — Psalms 89:25 (ASV)

I will set his hand also in the sea

Which is expressive not of his dominion over the sea, and of his power and authority over all things in it, which: he has by right of creation, and as Mediator, (Psalms 8:5–7) , of which there were instances in the days of his flesh, (Matthew 8:26Matthew 8:27) (17:27) , but of his kingdom taking place in, and of his government over the inhabitants of the isles of the sea; and so the Targum,``I will set or place his government in the provinces of the sea;'' and which has been remarkably accomplished in our isles, where his Gospel has been preached, his kingdom set up, and he has had a race of subjects, and a seed, to serve him for many years:

and his right hand in the rivers :

or, as the Targum,``the power of his right hand in those that dwell by rivers;'' meaning such that dwell upon the continent, afar off from the sea, and whose countries are watered by rivers: so that both phrases denote the extent of Christ's kingdom in the continent, and in the islands of the sea; signifying, that it should reach everywhere, and be from sea to sea, and from the river to the ends of the earth, (Psalms 72:8) . Compare with this (Revelation 10:1Revelation 10:2) . Aben Ezra interprets it of David's prevailing over those that go in ships in the sea, and in rivers.