28:23-29 The husbandman applies to his calling with pains and prudence, in all the works of it according to their nature. Thus the Lord, who has given men this wisdom, is wonderful in counsel, and excellent in his working. As the occasion requires, he threatens, corrects, spares, shows mercy, or executes vengeance. Afflictions are God's threshing instruments, to loosen us from the world, to part between us and our chaff, and to prepare us for use. God will proportion them to our strength; they shall be no heavier than there is need. When his end is answered, the trials and sufferings of his people shall cease; his wheat shall be gathered into the garner, but the chaff shall be burned with unquenchable fire.

29. This also—The skill wherewith the husbandman duly adjusts his modes of threshing is given by God, as well as the skill (Isa 28:26) wherewith he tills and sows (Isa 28:24, 25). Therefore He must also be able to adapt His modes of treatment to the several moral needs of His creatures. His object in sending tribulation (derived from the Latin tribulum, a "threshing instrument," Lu 22:31; Ro 5:3) is to sever the moral chaff from the wheat, not to crush utterly; "His judgments are usually in the line of our offenses; by the nature of the judgments we may usually ascertain the nature of the sin" [Barnes].