John Calvin Commentary Psalms 65:6

"Who by his strength setteth fast the mountains, Being girded about with might;" — Psalms 65:6 (ASV)

By his strength setting fast the mountains. For the sake of illustration, he uses as an example the power of God seen in the general fabric of the world. In those times, it sounded like a new and strange truth to say that the Gentiles would be called to the same hope as the Jews.

To prove that it was not as incredible as they were inclined to imagine, the Psalmist very appropriately refers to the divine power apparent in all parts of the world. He points to the mountains rather than the plains, because the immense masses of earth and the lofty rocks they present convey a more impressive idea of the Godhead.

Interpreters do not agree on the exact meaning of the following verse. Some think that a word indicating comparison (like "as" or "like") must be mentally added before the first word of the sentence. They believe it means that God stills the tumults of men when they are raging in their insolent attempts, just as He stills the agitations of the sea. Others understand the first part of the verse to be a metaphorical statement of what is plainly declared at its end.

I would take the words simply as they stand. I consider that in the first part of the verse, David refers to the illustration of divine power we see in the sea, and in the second part, he refers to what we see in God's actions among men.

God's strength is shown in calming the waves and the stormy surgings of the ocean. It is also demonstrated in suppressing disturbances that may have been stirred up by the people.