And we must note these three degrees, that the promise was first made to the Jews, and then to their children, and last of all, that it is also to be imparted to the Gentiles. We know the reason why the Jews are preferred before other people; for they are, as it were, the first begotten in God’s family, yea, they were then separated from other people by a singular privilege. Therefore Peter observeth a good order, when he giveth the Jews the pre-eminence. Whereas he adjoineth their children unto them, it dependeth upon the words of the promise: I will be thy God, and the God of thy seed after thee, (Gen. 17:7,) where God doth reckon the children with the fathers in the grace of adoption.
This place, therefore, doth abundantly refute the manifest error of the Anabaptists, which will not have infants, which are the children of the faithful, to be baptized, as if they were not members of the Church. They espy a starting hole in the allegorical sense, and they expound it thus, that by children are meant those which are spiritually begotten. But this gross impudency doth nothing help them. It is plain and evident that Peter spake thus because God did adopt one nation peculiarly. And circumcision did declare that the right of adoption was common even unto infants. Therefore, even as God made his covenant with Isaac, being as yet unborn, because he was the seed of Abraham, so Peter teacheth, that all the children of the Jews are contained in the same covenant, because this promise is always in force, I will be the God of your seed.
—John Calvin, Commentary upon the Acts of the Apostles, trans. Henry Beveridge (repr. Bellingham, WA: Logos Bible Software, 2010), 1,122–23.