Jamieson, Fausset and Brown on 2 Kings 13:7

7. made them like the dust in threshing--Threshing in the East is performed in the open air upon a level plot of ground, daubed over with a covering to prevent, as much as possible, the earth, sand, or gravel from rising; a great quantity of them all, notwithstanding this precaution, must unavoidably be taken up with the grain; at the same time the straw is shattered to pieces. Hence it is a most significant figure, frequently employed by Orientals to describe a state of national suffering, little short of extermination (Is 21:10; Mi 4:12; Jr 51:33). The figure originated in a barbarous war custom, which Hazael literally followed (Am 1:3, 4; compare 2Sa 18:31; Jud 8:7).

2Ki 13:8-25. Joash Succeeds Him.