Paul links his rejection of boasting (3:27–31) with Abraham, whom he describes as the fundamental paradigm for God’s people, the prototype of justification for both Gentiles and Jews. Paul argues in 4:1–16 that Abraham was justified by God not on the basis of works but on the basis of faith. Abraham was regarded as the first converted Gentile (from Ur of the Chaldeans, Gen. 15:7) and as the first Jew who was circumcised and received God’s covenant (Genesis 15; 17). Contrary to the traditional Jewish understanding of Abraham, Paul argues that Abraham, as the Jews’ ancestor according to the flesh (4:1; NIV “our forefather”), discovered that he was not justified on the basis of his works. His works provided him with claims for boasting before human beings “but not before God” (4:2).

Paul re…