John Calvin Commentary Isaiah 42:9

"Behold, the former things are come to pass, and new things do I declare; before they spring forth I tell you of them." — Isaiah 42:9 (ASV)

The former things. He now recalls the former predictions, by the fulfillment of which he shows that confidence ought to be placed in him for the future; for what we have known by actual experience ought greatly to confirm our belief. It is as if he had said, “I have spoken so frequently to your fathers, and you have found me to be true in all things; and yet you cannot place confidence in me about future events: the experience of past transactions produces no effect on you and does not motivate you to do better.” God’s favors, therefore, ought to be mentioned by us in such a way that, whenever our salvation lies concealed in hope, we may rest on the word of God and be confirmed by it throughout our entire lives.

Behold! they came. By the adverb behold, he points out, as with a finger, that they had learned by experience that God is not false and did not speak in vain through the prophets, because clear proofs openly testified and proclaimed the truth of God.

Before they spring forth. He distinguishes God from idols by this mark: that he alone knows and predicts future events, but idols do not know them. Regarding the greater part of the responses that were given by the gods of the Gentiles, we have previously seen that they were either false or ambiguous, for those who relied on them were often shamefully deceived, and this is the reward they richly deserved.

And if at first sight the event corresponded, this plunged them deeper into eternal perdition; and by the righteous judgment of God, it was brought about that Satan deceived them with such delusions. It was far different with the sacred oracles, by which the Church, for her own advantage and salvation, was at one time brought to repentance and at another time encouraged to entertain favorable hope, so that she might not sink under the burden of punishments. It remains a settled principle that all that God has foretold is verified by the event, for he rules and directs all things by his providence.