Our culture today cares little about the past; “progress” is its main concern. In ancient days, however, such was not the case. People tended to be wary of new things. Because of Judaism’s ancient faith, many Gentiles respected it, despite the fact that many were also suspicious of the Jews. If a rabbi wanted to make converts to the Mosaic law, appealing to the oldest parts of the Jewish religion to defend his position was a great way to attract followers. This is what the Galatian Judaizers did when they used Abraham as a model of one put right with God by works of the Law, especially circumcision (Gen. 17).
Paul’s reply proves that Abraham and all other sinners are declared righteous only by faith, because no one obeys our Creator perfectly (Gal. 3:1–9). All sinned in Adam (Rom. 5:12–21), and even the Jews, who saw clearly what God requires in the Mosaic law, confirmed the curse on mankind in failing to do the works of the Law (Gal. 3:10–12). Jesus never broke the Law (1 Peter 2:21–23), earning righteousness for all who believe. On the cross, our sins were imputed to Him, and when we believe, His perfect record is imputed to us, and our curse is removed (Gal. 3:13–14). Luther comments on Galatians 2:16 that faith “justifies because it apprehends and possesses this treasure, even Christ present.”
The primacy of faith is developed in today’s passage through an appeal to the chronological sequence of the Abrahamic and Mosaic covenants. Since man-made agreements are not annulled or changed once sworn, how much more are the covenants of God inalterable (3:15)? Long before ratifying His covenant with Moses, our Creator promised an inheritance to Abraham, and nothing can add to or change it. If Abraham and his offspring receive it by faith alone, then it is received by faith alone forever, no matter the later covenants.
The promise made to Abraham’s offspring was made not to a multitude, but to one — Christ (v. 16). Paul has not misread Genesis, he knows that “offspring” is a collective singular that means many individuals (v. 29). But Jesus is the offspring of faith par excellence, for only He was utterly obedient to the Father. Therefore, we are blessed as Abraham’s offspring only if we are in Christ Jesus.