The truth of ‘born again’ Christians being the only People of God is summed up in a single sentence: Christ called a people together made up of Jews and Gentiles which would be one, not according to the flesh, but in the Spirit, and they would be the people of God.
Jesus Christ has made his followers into the whole People of God. The ministry of Jesus was to bring into existence a renewed people, in continuity with the Israel of old. Paul calls this new community ‘the Israel of God’. Galatians 6:16
Jesus symbolized his intention to do this by choosing the Twelve, Matthew 10:1-8, as representatives of the twelve tribes of Israel and as the foundation members of a renewed and mission minded community. Just as the Covenant on Sinai was the centre of Old Testament religion, so Jesus made the new Covenant in his blood the centre of the religion of the Christian People of God. The accounts of the New Covenant in the blood of Jesus, as expressed in his action and words with the cup of wine at the Last Supper, are parallel to those which tell of the making of the Sinai Covenant in Exodus 24:8
Christ instituted this new Covenant in his blood and He called a people together made up from people of every tribe, race, nation and language, Revelation 5:9-10, who would be one, not according to the flesh, but in the Spirit, and they are now the Christian people of God.
This expanded People of God are bonded together by the sacrifice of the life of Jesus and the gift of his Spirit dwelling in their hearts, re-creating, directing, activating and motivating them from within. Paul’s letter to Titus speaks clearly of the influence of the Holy Spirit given at the rite of baptism, the first sacrament of Christian initiation: From the goodness and loving kindness of God; our Saviour appeared and He saved us, not because of any works of righteousness that we had done, but according to His mercy, through rebirth and renewal by the Holy Spirit. This Spirit he poured out on us richly through Jesus Christ our Saviour, so that, having been justified by his grace, we would become heirs according to the hope of eternal life, Titus 3:5-7
The clearest expression of the identity of the People of God of the New Covenant is found in 1 Peter 2:9-10 But you are a chosen race, a royal priesthood, a holy nation, God’s own people, in order that you may proclaim the mighty acts of him who called you out of darkness into his marvellous light. Once you were not a people, but now you are God’s people; once you had not received mercy, but now you have received mercy.
Romans 9:24-25 We [Christians] are the recipients of God’s mercy, whom He has called from among the Jews and Gentiles, for as Hosea says: Those who were not My people, I will call My people…..sons of the Living God. a