How do we know that believers are the true Israel of God?

The New Testament clarifies that the true Israel is not limited to ethnic descendants of Abraham but includes all who have faith in Christ. In Galatians 3:29, Paul writes that if we belong to Christ, we are Abraham's seed and heirs according to the promise. This means that God’s covenantal blessings are extended to all who are united with Christ, establishing a new identity as His chosen people. This transition signifies the unfolding of God's plan where the mystery of the Gospel is revealed, uniting Jews and Gentiles as one body in Christ.