John Calvin Commentary Isaiah 66:18

"For I [know] their works and their thoughts: [the time] cometh, that I will gather all nations and tongues; and they shall come, and shall see my glory." — Isaiah 66:18 (ASV)

For I — their works, and their thoughts. He confirms what he said in the preceding verse: namely, that punishment will be executed on all the ungodly, so that, although the Lord permits them for a time to sin with impunity, believers, being convinced that they will one day be punished, may guard against following their example.

The Lord here testifies that he sees and observes their works, and that one day he will actually manifest that none can be concealed from his eyes. Others understand it to mean that the ungodly can accomplish nothing without God’s permission.

That statement is indeed true but is not applicable to this passage. For everyone sees that it is unnatural and at variance with the Prophet's context, who merely confirms what he previously said: that hypocrites and wicked men will not finally escape with impunity, because God perceives all their actions, schemes, and thoughts, and that they gain nothing by their evasions, as if they were never to be dragged to judgment.

Because the time is come. These words further confirm what has already been said, for he says that the time is at hand when he will assemble all the nations, that he may cast off the hypocrites and ungodly, and gather and adopt a people for himself from among them. The Jews were puffed up with pride and despised all other nations as unholy. But the Lord declares that he will adopt those nations, so that they may be partakers of his glory, of which the Jews prove themselves to be unworthy.

This is a remarkable passage, teaching us that God is not confined to any people; he is free to choose whomever he pleases, casting off unbelievers whom he previously called to himself. This is abundantly explained by Paul (Romans 10:19; Romans 11:25), where he shows that we have come into a possession that was left empty after the Jews were cast off through their unbelief. Isaiah now threatens them in this manner: "Do not think that God is in need of peoples when you have revolted and made yourselves unworthy of his grace, for he will have others; but he will show that he is the judge and will not finally permit you to abuse such great forbearance."

And they shall come. He says that they shall come, because, being ingrafted by unity of faith, they will be united in the Church with the true Jews, who have not swerved from the adoption. For, since the Jews are near to God, the Gentiles, who were at a distance, must be joined to them, so that, by the removal of disagreement, they might become one body.

And shall see my glory. To see the glory of the Lord is nothing else than to enjoy that grace that he had bestowed on the Jews. For the special privilege of that nation was that they beheld the glory of God and had tokens of his presence. He says that now the Gentiles, who had not enjoyed these benefits, will see and behold that glory, for the Lord will reveal himself to all without exception.