Matthew 16:18
“I also say to you that you are Peter, and upon this rock I will build My church; and the gates of Hades will not overpower it.”
Calvinists will no doubt insist that by an alleged decree, the elect were hidden in Christ from before the foundation of the world, such that now God builds the church according to what was eternally foreordained. However, the Bible says that you are only hidden in Christ after you have died to self and have become a Christian: “For you have died and your life is hidden with Christ in God.” (Colossians 3:3) The only way to become hidden in God the Father is through becoming in the Son by faith. 1st John 2:24 states: “If what you heard from the beginning abides in you, you also will abide in the Son and in the Father.”
John Calvin comments: “It is as if He said, ‘You are now just a tiny number of men, and therefore your confession has little worth at present; but the time will soon come when it will stand out splendidly and will spread far wider.’ And this availed not a little to encourage the disciples to constancy; because, although their faith was obscure and lowly, yet they were chosen by the Lord as first fruits so that at last from this insignificant beginning there should arise the new Church which would stand triumphant against all the designs of hell.” (Calvin’s New Testament Commentaries, A Harmony of the Gospels: Matthew, Mark and Luke, Vol. II, p.186, emphasis mine)
That’s exactly right: the new Church. Not the old Church but the new Church as people are continually added to the roll of the Lamb’s Book of Life. Although we are chosen from before the foundation of the world, that is only a half truth since we are not chosen in ourselves but chosen in Christ, and we are not elect in Christ while we are lost and under condemnation in Adam but rather we are elect in Christ only when we pass out of condemnation (Romans 8:1, 33) as a twice born, regenerated new creature in Christ. (2nd Corinthians 5:17) No one is elect in Christ while as a once born, unregenerate old creature in self. The only way in which we could be elect in Christ before we were actually in Christ is by what the Bible refers to as the “foreknowledge of God the Father.” (1st Peter 1:1-2) Based upon this foreknowledge, God has predestined us to the everlasting glory that comes with being in Christ, just as described at Romans 8:29.