This is the end of a hypothetical statement that begins with the words "If Yahweh had not been on our side" in [Psalms 124:1](./001.md) and continues with the words "if it had not been Yahweh who was on our side when men rose up against us" in [Psalms 124:2](./002.md). It describes a result that did not happen because Yahweh was actually on their side. "The raging waters did not drown us because Yahweh was on our side" (See: [[rc://en/ta/man/translate/figs-hypo]])
Here the enemies of the writer are spoken of as if they were a raging river that would have drowned the Israelites. Alternate translation: "our enemies would have destroyed us" (See: [[rc://en/ta/man/translate/figs-metaphor]])