John Calvin Commentary 1 Peter 2:10

"who in time past were no people, but now are the people of God: who had not obtained mercy, but now have obtained mercy." — 1 Peter 2:10 (ASV)

Which in time past were not a people. He brings a passage from Hosea for confirmation and aptly applies it to his own purpose. For Hosea, after having declared in God’s name that the Jews were repudiated, gives them hope for a future restoration. Peter reminds us that this was fulfilled in his own age, for the Jews were scattered here and there, like the torn members of a body. Indeed, they seemed to be no longer God’s people: no worship remained among them, and they had become entangled in the corruptions of the pagans. It could not then be said of them otherwise than that they were repudiated by the Lord.

But when they are gathered in Christ, from being no people, they truly become the people of God. Paul, in Romans 9:26, also applies this prophecy to the Gentiles, and not without reason. For from the time the Lord’s covenant was broken (from which alone the Jews derived their superiority), they were put on a level with the Gentiles. Therefore, it follows that what God had promised—to make a people of no people—belongs in common to both.

Which had not obtained mercy. This was added by the Prophet so that the gracious covenant of God, by which He takes them to be His people, might be more clearly presented. It is as if he had said, “There is no other reason why the Lord considers us His people, except that He, having mercy on us, graciously adopts us.” It is, then, God’s gracious goodness, which makes of no people a people to God and reconciles the alienated.