John Calvin Commentary 1 Peter 1:20

"who was foreknown indeed before the foundation of the world, but was manifested at the end of times for your sake," — 1 Peter 1:20 (ASV)

Who verily was foreordained: He again, by a comparison, amplifies the grace of God, with which he had especially favored the people of that age. For it was not a common or a small favor that God deferred the manifestation of Christ to that time, even though he had ordained him in his eternal council for the salvation of the world.

At the same time, however, he reminds us that it was not a new or a sudden thing for God that Christ appeared as a Savior; and this is what should especially be known. For, in addition to this, because novelty is always suspicious, what would be the stability of our faith if we believed that a remedy for humankind had suddenly, after some thousands of years, finally occurred to God?

In short, we cannot confidently rely on Christ unless we are convinced that eternal salvation is in him and always has been in him. Besides, Peter addressed the Jews, who had heard that he had already been promised long ago. And though they understood nothing true, clear, or certain concerning his power and office, yet there remained among them a persuasion that a Redeemer had been promised by God to the fathers.

It may still be asked: Since Adam did not fall before the creation of the world, how was it that Christ had been appointed the Redeemer? For a remedy comes after the disease. My reply is that this relates to God’s foreknowledge. For undoubtedly God, before he created man, foresaw that he would not stand long in his integrity. Therefore, he ordained, according to his wonderful wisdom and goodness, that Christ should be the Redeemer, to deliver the lost human race from ruin. For in this, the unspeakable goodness of God shines forth more fully, in that he anticipated our disease with the remedy of his grace and provided a restoration to life before the first man had fallen into death. If the reader wishes for more on this subject, they may find it in my Institutes.

But was manifest, or manifested: I think that included in these words is not only the personal appearance of Christ but also the proclamation of the Gospel. For by the coming of Christ, God executed what he had decreed; and what he had obscurely indicated to the fathers is now clearly and plainly made known to us by the Gospel. He says that this was done in these last times, meaning the same as when Paul says,

“In the fullness of time” (Galatians 4:4).

For it was the mature season and the full time which God in his counsel had appointed.

For you: He does not exclude the fathers, to whom the promise had not been useless. But as God has favored us more than them, he intimates that the greater the abundance of grace toward us, the more reverence, ardor, and care are required of us.