I'll try to convey what I can concerning this difference. Paul emphasized the fact that both Jewish & Gentile Believers were of the same Spirit, however the Jewish Believers were under a covenant with God that recognized their national identity, whereas Gentile Believers remain outside any such consideration. God is still in the process of building a nation here on the Earth by way of the Jewish People. This is the main difference in God's Conenant with Believers of the two groups. God is not trying to form a Nation of the Gentile believers, therefore the term "Body of Christ". Even when reading the new Testament scriptures this difference should be considered. No doubt most people would probably agree that alot of Old Testament Scriptures have a different application depending on the reader, whether they are Jewish or Gentile. The same can be said of alot of the New Testament. Some Epistles are written to mainly Jewish Believers and others to predominatly Gentile Believers. This isn't to say that Jewish and Gentile Belivers can't work together, since both groups have the same Spirit and the same God, but their roles in God's plan are different. Different roles would possibly mean different instructions. Consider any organized project, and you might find the same situation exists, Different instructions to all involved according to their relationship with the builder. I'm no Scholar of the bible and would advise anyone to check into the idea for themself & I think Bob Enyart has some good information on this subject but I wouldn't exclude any other source of information. Thanks for you'r time.