What does Romans 9:29 mean?
In the previous verses, Paul quoted from Isaiah 10 to prove several points. First, God has kept His promises to Israel. Second, God never promised to eternally save everyone physically born into Israel. Third, God has called out a remnant from among the Jews to be saved through faith in Christ.Now Paul emphasizes this idea that a remnant will be saved; highlighting the fact that God has not and will not wipe out Israel completely no matter how faithless she has been, by quoting from Isaiah 1:9. Sodom and Gomorrah were judged by God so severely that they were utterly removed from the earth (Genesis 19:24–25). With Israel, though, the Lord of hosts has always spared some from the next generation to carry on as Israel, no matter how severe God's judgment became.
Paul is making the significant claim that God will continue to spare a remnant, now by calling some of the Jewish people out from among the rest through faith in Christ.