"For he is not a Jew who is one outwardly . . . but he is a Jew who is one inwardly . . . "
Paul here (above) affirms that the true Jew is one who believes in Jesus--be he or she a Jew or a Gentile (by ethnicity). All of the Old Testament Jewish believers put their trust in Jesus (though they didn't yet know His name). The same is true in the New Testament, and in the era of the New Covenant (in which we currently live).
The "new" "Israel of God," the New Covenant church (cf. Gal. 6:16b), is made up of Jews *and* Gentiles, and they are all the authentic sons of Abraham, the father of our faith. Let us (especially who were Gen-
tiles by birth) thank God that He has ingrafted us into the Vine of Christ.
[Puritan quote of the day: "If the church is beautiful beyond all other of the children of men, how beautiful is Jesus Christ, from whom the church derives all its comeliness?" --Thomas Vincent, in, "The True Christian's Love to the Unseen Christ"]