Q. I’m confused by Romans 9:6-8, We know that Jacob is Israel and also Isaac’s son, so aren’t all of Jacob’s descendent also those of Isaac? What is meant by “For they are not all Israel which are descended from Israel”? Does this imply some Jews are not Jews?
A. This ties in with Paul’s earlier comment in Romans 2:28-29;
“A person is not a Jew who is one only outwardly, nor is circumcision merely outward and physical. No, a person is a Jew who is one inwardly; and circumcision is circumcision of the heart, by the Spirit, not by the written code. Such a person’s praise is not from other people, but from God.”
In effect he was saying that from God’s perspective being a Jew is not merely biological, it’s also spiritual. Jewish people who do not accept the pardon the Lord purchased for them with His own blood will share the same destiny as unbelieving Gentiles, their Jewish bloodline notwithstanding.