John Calvin Commentary Isaiah 29:5

"But the multitude of thy foes shall be like small dust, and the multitude of the terrible ones as chaff that passeth away: yea, it shall be in an instant suddenly." — Isaiah 29:5 (ASV)

And as the small dust. I will first state the opinions of others, and afterwards I will bring forward what I consider more probable. Almost all the commentators think that this expression denotes the enemies of the Jews; for they consider “foreigners” to mean “enemies,” and allege that the multitude of those who will oppress the Jews will be “like dust;” that is, it will be innumerable. But when I examine the whole passage closely, I am more inclined to adopt a contrary opinion. I think that the Prophet speaks contemptuously of the garrisons on which the Jews foolishly relied, for they had in their pay foreign soldiers who were strong men.

The multitude of the mighty ones. This is the interpretation I give to עריצים (gnărītzīm), which is also its literal meaning; and I see no reason why some of the Jews should suppose it to mean ungodly or wicked persons. Since, therefore, the Jews brought various garrisons from a distance, they thought that they were well defended and dreaded no danger. The Prophet threatens that their subsidiary troops, though they were a vast multitude, will in vain create a disturbance, for they will be like “dust” or “chaff,” that is, useless refuse, for they will produce no effect.

Therefore, we ought to infer that our wealth and resources, however great they are, will be reduced to nothing as soon as the Lord determines to deal with us as He has a right to do. The assistance of men lasts indeed for a time; but when the Lord lifts up His hand in earnest, their strength must crumble down, and they must become like chaff.

And it shall be in a moment suddenly. Some explain the concluding clause of this verse to mean that the noise of the enemies’ attack will spring up suddenly and, as it were, in a moment. But I consider והיה (vĕhāyāh), and it shall be, to relate to the time of duration, which he declares will be momentary; that is, those military aids will not last long, but will quickly vanish away. In vain do men boast of them, for God is their enemy.