John Calvin Commentary Isaiah 21:17

"and the residue of the number of the archers, the mighty men of the children of Kedar, shall be few; for Jehovah, the God of Israel, hath spoken it." — Isaiah 21:17 (ASV)

And the residue of the archers. He threatens that this slaughter will not be the end of their calamities, because if there is any residue in Arabia, they will gradually decrease. It is as if he had said, “The Lord will not merely impoverish the Arabians by a single battle, but will pursue them to the very end, until all hope of relief is taken away, and they are utterly exterminated.” Such is the vengeance He executes against the ungodly, while He moderates the punishment He inflicts on the godly, so that they may not be entirely destroyed.

Of the mighty men. He means warlike men and those who were fit to carry arms, and says that although they escaped that slaughter, they will still be cut off at their own time. He formerly threatened similar chastisements against the Jews, but always accompanied by a promise suited to alleviate their grief or at least to guard them against despair. It frequently happens that the children of God are afflicted as severely as the reprobate, or even with greater severity. However, the hope of favor that is offered distinguishes them from the whole world. Again, when we learn that God inflicts deadly vengeance on the wicked, this is no reason for us to be excessively grieved even at the heaviest punishments. On the contrary, we should draw this consolation from it: that He chastises them gently and does not give them over to death (Psalms 118:18).

The God of Israel hath spoken it. The Prophet shows, as we have frequently remarked on former occasions, that we should not only acknowledge that these things happened by divine appointment, but also that they were appointed by that God whom Israel adores.

All men are sometimes constrained to acknowledge God, even though they may be disposed to believe in chance. This is because the thought that there is a God in heaven enters their minds, whether they will it or not, both in prosperity and in adversity. However, they then imagine a Deity according to their own fancy, either in heaven or on earth.

Therefore, since irreligious men idly and foolishly imagine a God according to their own pleasure, the Prophet directs the Jews to that God whom they adore, so that they may know the distinguished privilege they enjoy in being placed under His guardianship and protection.

Nor is it enough that we adore some God as governor of the world; we must acknowledge the true God, who revealed Himself to the fathers and has manifested Himself to us in Christ.

And this truth should be earnestly maintained against the profane thoughts of many people who contrive some strange and confused notion of a Deity because they dare not openly deny God.