ישעיהו יז:יג פירוש: רש״י ואבן עזרא

and He shall rebuke them [lit.] him i.e., the Holy One, blessed be He, [shall rebuke] that rushing [or throng].

But He shall rebuke him. God will rebuke the king of Assyria.

like the chaff of the mountains He likens the wicked to the most inferior of all species and the most inferior of that species. The chaff of the mountains is drier than that of the valleys.