Charles Ellicott Commentary Psalms 46:3

"Though the waters thereof roar and be troubled, Though the mountains tremble with the swelling thereof. Selah" — Psalms 46:3 (ASV)

Though the waters ... —The original is very expressive in its conciseness:

“They roar, they foam, its waters.”

Compare Homer’s equally concise description, including in three words the “rush,” the “swell,” and the “roar” of ocean (Iliad, 23.230).

Swelling. —Or, pride. (Compare Job 38:11.) The change in construction in this verse seems to confirm the suspicion that the refrain has dropped away.