Jesus’ parable of the wicked tenants (Matthew 21) exposed the religious leaders who rejected the cornerstone, while His declaration that many would come from east and west to feast with Abraham (Matthew 8:11-12) warned that ethnic descent from Abraham does not guarantee a place in the kingdom. Paul takes up the same truth in Romans 9: God’s word has not failed, because not all who are descended from Israel are true Israel; it is the children of the promise, not merely the children of the flesh, who are counted as Abraham’s offspring.
Paul even calls Israel’s own stumbling over Christ a fulfillment of that pattern, pursuing righteousness by works rather than by faith, while Gentiles who did not pursue it attained it through faith. Reading Genesis’s two sons, of the bondwoman and the free woman, allegorically in Galatians 4, Paul shows that the true children of promise are heirs through faith in Christ, not human descent, so that all who belong to Christ, Jew and Gentile alike, are Abraham’s true seed.