How do we know that not all of Israel is saved?

In Romans 9, Paul addresses the apparent discrepancy between God's promises to Israel and the reality that not all descendants of Abraham are saved. He states that not all who are physically descended from Israel belong to the true Israel of God, which consists of the elect—those chosen by God for salvation. This teaches us that God's election is based on His sovereign choice, not on ethnicity or human merit. Thus, the true Israel encompasses all who believe in Christ, affirming that salvation is a matter of God’s grace and calling rather than human lineage.