And he carried me away in the Spirit to a great, high mountain, and showed me the holy city Jerusalem coming down out of heaven from God, having the glory of God, its radiance like a most rare jewel, like a jasper, clear as crystal. It had a great, high wall, with twelve gates, and at the gates twelve angels, and on the gates the names of the twelve tribes of the sons of Israel were inscribed— on the east three gates, on the north three gates, on the south three gates, and on the west three gates. And the wall of the city had twelve foundations, and on them were the twelve names of the twelve apostles of the Lamb.

Revelation 21:10-14

Now we begin to see the beauty of this Holy City. Notice the names of the tribes of Israel on the gates and the names of the twelve apostles on the foundations. If this New Jerusalem is the Church, then that description should sound instantly familiar:

So then you are no longer strangers and aliens, but you are fellow citizens with the saints and members of the household of God, built on the foundation of the apostles and prophets, Christ Jesus himself being the cornerstone, in whom the whole structure, being joined together, grows into a holy temple in the Lord.

Ephesians 2:19-21

Both Paul and John understand the Church contains both the Old and New Covenant believers within its "walls." There is only one Way of salvation. Repentance and faith in Christ.