In Romans 4, Paul sets Abraham before his audience for consideration. Why does he do this? Is it to give an Old Testament example of justification by faith? Not exactly.
Following the grammar in vv. 13-16, it’s apparent that Paul calls upon Abraham to advance his argument that the divided factions in the Roman church must be unified.
It’s not too fanciful to imagine that Paul sends Abraham to Rome to visit the church(es). He sets him squarely within the divided Roman church(es), provoking the question of which side can claim the support of Abraham against the other. Whose side is he on? For whom is he a cheerleader?
The Jewish-Christian faction would immediately assume he would support their case for privileged status in the Roman church(es). After all, a number of Jewish texts portray Abraham as the ideal Law-observer.
Do they have a case? Can they so easily assume that Abraham would endorse their claims?
Well, let’s take a look, says Paul. Was Abraham justified by deeds that distinguish a person as a faithful Jew?
While Paul does not use the phrase “works of Law” in v. 2, he is still referring to such works. The tension between Jewish and non-Jewish Christians dominates Romans 1-3 and leads into this discussion in Romans 4. And Paul returns to Abraham’s relation to the circumcised and uncircumcised in v. 9. Since this problem frames the passage, it’s likely that Paul has it in mind here, too.
If Abraham were justified by faithfully embodying Jewish identity, then he can boast alongside the Jewish Christians over-against the non-Jewish Christians.
Paul makes clear in v. 2 that he isn’t speaking about boasting “before God.” He still has in view the boasting of one group over another from a few verses earlier (Rom. 3:27).
If Abraham was justified by deeds that indicate faithfulness to Jewish identity, then he takes one side in the conflict in Rome.
Paul cites Gen. 15:6, which states that Abraham believed God and that God reckoned Abraham righteous because of his faith. And this was before Abraham was circumcised (v. 10).
After that, however, Abraham was circumcised so that he might be the father of the uncircumcised believers and the circumcised believers (vv. 11-12).
When Paul sends Abraham to Rome, therefore, Abraham puts his arms around everyone—all those of faith, without reference to their being Jewish or non-Jewish.
Abraham doesn’t take sides in the Roman conflict. No side can claim Abraham because Abraham claims everyone!
God promised Abraham that he’d be the agent of universal blessing, and God fulfills his promise only by his grace. Because it is by grace, it can only be received by faith. No group can claim exclusive rights to the blessing by belonging to any singular ethnicity. That would eliminate the gracious character of God’s promise.
God’s blessing is enjoyed by faith so that the promise can maintain its character as grace, “so that the promise will be guaranteed to all the descendants, not only to those who are of the Law, but also to those who are of the faith of Abraham, who is the father of us all” (v. 16).
Paul sends Abraham to Rome not to serve as an example of the abstracted concept of justification by faith, but to unify the church.