What distinction is Paul making between Jews, Gentiles, and members of the Body of Christ?
Paul distinguishes Jews and Gentiles from one another, and he further distinguishes those Jews and Gentiles who are members of the Body of Christ. So the contrast is not simply Jew versus Gentile, but also Jew and Gentile as such versus those who belong to the Body of Christ.
Les explains that Paul’s letters are a progressive revelation. At this point Paul is still showing that there is a difference between the Jew and the Gentile, and also between those Jews and Gentiles who were members of the Body of Christ. This distinction runs alongside Paul’s overriding concern for lost people, for whom Christ paid the sin debt, shed His blood, and was raised.