13. shall … shall—rather, "God rebuketh (Ps 9:5) them, and they flee—are chased"; the event is set before the eyes as actually present, not future.
chaff of … mountains—Threshing floors in the East are in the open air on elevated places, so as to catch the wind which separates the chaff from the wheat (Ps 88:13; Ho 13:3).
rolling thing—anything that rolls: stubble.