A Biblical Mystery: Christians need to become a Jew! What does this mean?

I wrote the title of this book to get people's attention. It is true, but you need to read the rest of the story to understand who said it and why.So, what does it mean, Christians need to become a Jew? Apostle Paul is the one that said it. It is in Romans 2:28-29: "For he is not a Jew, which is one outwardly; neither is circumcision, which is outward in the flesh. But he is a Jew, which is one inwardly..."Why did Paul say this? What does it mean to be "a Jew inwardly"?When you understand what Paul is talking about, you will see the Gospel in an entirely new light. You will also understand many Bible scriptures that you never understood before.