Jamieson, Fausset and Brown on Joel 3:13

13. Direction to the ministers of vengeance to execute God's wrath, as the enemy's wickedness is come to its full maturity. God does not cut off the wicked at once, but waits till their guilt is at its full (so as to the Amorites' iniquity, Ge 15:16), to show forth His own long-suffering, and the justice of their doom who have so long abused it (Mt 13:27-30, 38, 40; Re 14:15-19). For the image of a harvest to be threshed, compare Jr 51:33; and a wine-press, Is 63:3 and La 1:15.