John Calvin Commentary Isaiah 17:9

"In that day shall their strong cities be as the forsaken places in the wood and on the mountain top, which were forsaken from before the children of Israel; and it shall be a desolation." — Isaiah 17:9 (ASV)

In that day shall his strong cities be as a forsaken bough. He continues what he had begun to say about driving out the inhabitants of the country. As the Israelites, trusting in their fortified cities and their bulwarks, thought they were safe, he threatens that these will be of no more use than if enemies were marching through desert places. The view held by some, that חורש (chōrĕsh) and עזובת (ăzūbăth) are proper names of towns, is a forced interpretation. I understand them rather to denote unpleasant and disagreeable places, or that the walls and ditches will contribute no more to their defense than if the Israelites dwelt among thickets and bushes.

As they left. Here the particle אשר, (asher,) I have no doubt, denotes comparison. Therefore, I have rendered it in like manner as, which makes the Prophet’s statement to be, in connection with what had already been said, that the people would tremble, flee, and be scattered, in the same manner as God had formerly driven out the ancient inhabitants.

Those who think that אשר, (asher,) is a relative are constrained to supply something and to break the thread of the discourse. But it simply reminds them of an ancient example, so that the Israelites may perceive how vain and deceitful every kind of defense is that is opposed to the arm of God.

It is a severe reproach, for the Israelites did not consider that the Lord gave them that land, as it were, by hereditary right, so that they might worship Him, and that He drove out their enemies to put them in possession of it. And now, by their ingratitude, they rendered themselves unworthy of so great a benefit. Consequently, when they had been deprived of it, it was right that they should experience distresses that were the reverse of their former blessings.

This passage will be made clearer by the writings of Moses, whom the prophets follow. For in the promises he uses this expression, One of you shall chase a thousand, (Leviticus 26:8; Joshua 23:10), and in the threats, on the other hand, he says, One shall chase a thousand of you. (Deuteronomy 32:30). Accordingly, just as He struck such terror into the Canaanites that at the sight of the Israelites they immediately fled, so He punished the ingratitude of the people in such a way that they had no power to resist.

Thus the Lord displayed His power in two ways: both in driving out the Canaanites and in punishing His people. The Prophet, therefore, by mentioning that ancient kindness, reproaches the people with ingratitude, forgetfulness, and treachery, so that they may acknowledge that they are justly punished and may perceive that it proceeds from the Lord, that they are thus chased by the enemies to whom they were formerly a terror.