"The promise to Abraham and his offspring that he would be heir of the world did not come through the law but through the righteousness of faith. For if it is the adherents of the law who are to be the heirs, faith is null and the promise is void" (vv. 13–14).
Chronology plays a key role in Paul's case for justification by faith alone. The Apostle proves that since God justified people by faith alone both before and after the old covenant law was revealed to Moses, this law cannot be the means by which sinners are justified. In Galatians 3, Paul notes that Abraham was justified through faith in the Lord's promise before the law was given. We have seen in Romans 4:1–12 that because the patriarch was declared righteous prior to being circumcised, one is justified by faith apart from works. Moreover, the Apostle argues that even those who lived after the law was given were justified by faith alone. David lived during the administration of the Mosaic law—after it was given—but faith alone was the means by which his sins were not imputed to him (vv. 6–8).
In today's passage, Paul turns from chronology to consider why righteousness before God comes only through faith, not works. Recall that many first-century Jews saw Abraham as the example of obedience par excellence and believed that his offspring earned their position by their law-keeping. The Apostle alludes to this belief in verse 13, using heir of the world to describe collectively the promise to Abraham—land, descendants, and blessings such as his enemies' defeat (Gen. 12:1–3; 22:15–18). These rewards, which come only to those whom God declares righteous, were Abraham's because he trusted in the Lord alone (15:6).
God's promise is through faith because "if it is the adherents of the law who are to be the heirs, faith is null and the promise is void" (Rom. 4:14). In line with Romans 1–3, the "adherents of the law" are not Jewish believers in Jesus but Jews who trust in their law-keeping for their righteousness. The promise is void if these Jews are justified by doing the commandments, because while one could be justified by keeping the law perfectly, no sinner can keep the law perfectly (2:13; 3:9–20). Martin Luther comments on 4:14, noting our inability to keep the law to the extent required for justification: "If the promise were through the Law, since it works wrath, it would follow that the promise is not a promise, but rather a threat." Along the same lines, Dr. R.C. Sproul writes in his commentary Romans, "If we seek to base our salvation on our merit, the only thing we will ever merit is God's wrath."
The law cannot produce any inheritors or heirs of God's promise because in regard to sinners' justification, the law brings only wrath (v. 15). It intensifies sin, creating boundaries that make us all the more guilty when they are transgressed.
Coram Deo
Romans 5 and 7 further develop the role of the law in regard to justification and its purpose in intensifying sin. For now it is enough to note that faith and works of the law are opposed in justification because even the good we do still falls short of God's glory. Thus, to seek justification by the law invalidates God's promise; it makes it impossible for sinners to find peace with the Lord because sinners cannot obey God perfectly. We look not to the law for our inheritance but to Christ.
