Thus saith the Lord, &c.— Thus saith the Lord to those who rule over many waters: as the waters are many, so shall they be carried away, and passed through. I will so afflict thee, as to afflict thee no more. The prophet calls the people waters, as is usual in the prophetic style, and because these waters had lately overflowed Judaea and the neighbouring countries. Houbigant.
Related Commentaries of Nahum 1:12
12 Thus saith the LORD; Though they be quiet,e and likewise many, yet thus shall they be cut down, when he shall pass through. Though I have afflicted thee, I will afflict thee no more.