Paul is making the argument that the things in the Old Covenant were only shadows of things in the New. The Jews were not those who were circumcised in the flesh because it never produced obedience to the law. The true circumcision was of the heart which did produce different behavior. Judah means praise and the man Judah who caused Leah to praise God was only a shadow of those who had faith. Those who have faith receive praise not from men, but from God because of the good works produced by their circumcised hearts.