So you believe this:
The completed form of the Jewish religion is known as
Christianity, and its adherents are
Christians or "followers of the Christ." Unfortunately, many people who were ethnically Jewish did not recognize Jesus’ role as Messiah and so did not accept Christianity, the completed form of Judaism. Instead, they stayed with a partial, incomplete form of Judaism. Other Jews (the apostles and their followers) did recognize that Jesus was the Messiah and embraced the new, completed form of Judaism.
Shortly thereafter it was recognized that one could be a follower of Christ even if one did not ethnically join the Jewish people. Thus the apostles began to make many Gentile converts to the Christian faith. It is thus possible for a person to be a Jew religiously (because he has accepted Christianity, the completed form of the Jewish faith) but not be a Jew ethnically. This is the case with most Christians today.
It is this difference between being a Jew ethnically and religiously that lies behind Paul’s statement in Romans 2:28-29: "For he is not a real Jew who is one outwardly, nor is true circumcision something external and physical. He is a Jew who is one inwardly, and real circumcision is a matter of the heart, spiritual and not literal."
If Jesus was a Jew, why are we Catholic? | Catholic Answers