It was in his letter to the Romans, however, that St. Paul laid the foundations for the medieval Church's attitude toward the Jews. There he wrote:Romans 11:18
Do not be arrogant toward the branches. If you are, remember it is not you who support the root, but the root that supports you.
Let me put a further question then: is it possible that God has rejected his people? Of course not. I, an Israelite, descended from Abraham through the tribe of Benjamin, could never agree that God had rejected his people, the people he chose specially long ago.[Romans 11:1-2]
If they were not rejected, then:
... have the Jews fallen for ever, or have they just stumbled? Obviously they have not fallen forever: their fall, though, has saved the pagans in a way the Jews may now well emulate. Think of the extent to which the world, the pagan world, has benefited from their fall and defection then think how much more it will benefit from the conversion of them all.[Romans 11:11-13].
In other words, by their refusal to accept Christ, the Jews had made it possible for the Gentiles to be saved. Paul is certain, though, that one day the Jews will see the truth (Romans 11:16-24). He concludes:
The Jews are enemies of God only with regard to the Good News, and enemies only for your sake; but as the chosen people, they are still loved by God, loved for the sake of their ancestors. God never takes back his gifts or revokes his choice.[Romans 11:28-29]