"For the fitches are not threshed with a threshing instrument, neither is a cart wheel turned about upon the cummin; but the fitches are beaten out with a staff, and the cummin with a rod. Bread corn is bruised; because he will not ever be threshing it, nor break it with the wheel of his cart, nor bruise it with his horsemen. This also cometh forth from the LORD of hosts, which is wonderful in counsel, and excellent in working." (Isaiah 28:27-29)
Being smaller and more delicate, cumin is not harvested in the same manner as wheat. The tiny bits of grain are removed from the plant by tapping them with a rod. The wheat however is threshed. This process is more violent. The Lord knows what each man and nation can handle. With the weak, He is more gentle; and with the strong and proud, He is more forceful. Israel could have found comfort in this. The Lord knew how to administer the appropriate amount of help and correction to her while dealing with the stronger nations of the world according to their strength and character.
Verse 28 is difficult to interpret. The main thought seems to be that of God's ability to bring chastisement while simultaneously preserving what is useful. The middle part of the verse literally reads, "He will not ever tread it to blood (of grapes) or gore." Even during the times of heavy chastisement when God sees fit to crush the grain, the end result is not in excess of that which is befitting the overall plan of God.
The passage ends with a declaration of God's unsearchable wisdom. Only He could exercise such skill and ability. The affairs of this world are far beyond the capabilities of any man; but the man who commits himself into the hands of the master Husbandman may rest quietly.