Summary: The promise granted through faith
In Galatians Paul argues hat Christ is the seed of Abraham, and so the blessing comes to the Gentiles as well as the Jews through Christ. The promise in Romans, this promise is not based on Abraham’s works or merits as in Galatians. Paul is following his argument chronologically by applying his theology in different contexts to give his readers, and us a clear understanding while not denying as well is other teachings. Paul’s way of thinking, a promise falls within the sphere of gift, that is of grace according to Barret, Romans, p.89. The promise has been given on the basis of the Law for works of the Law such as circumcision then it would be a contractual arrangement, and grace and faith would not enter in it. Thus, Paul reasons if heirs were heirs on the basis of the Law and works of the law, then faith and the promise would be in effect nullified (v.14). Faith, grace, and promise stand on one side of the ledger, and works, Law and sin stand on the other. This explanation is not sufficient by itself, so Paul adds the explanation that the Law causes wrath and that where there is no Law there is no transgression.
Romans 4: 13For the promise that he would be the heir of the world was not to Abraham or to his seed through the law, but through the righteousness of faith. 14For if those who are of the law are heirs, faith is made void and the promise made of no effect, 15because the law brings about wrath; for where there is no law there is no transgression.”
Just as Abraham was not justified by the rite of circumcision (vv.9-12), neither was he justified by keeping the Mosaic Law (vv.13-15). Promise.. heir of the world: This refers to Christ and is the essence of the covenant God made with Abraham and his descendants (Gen 12:3; 15:5; 18:18; 22:1. The final provision of that covenant was that through Abraham’s seed all the world would be blessed (12:3). Paul argues that “the seed” refers specifically to Christ and that this promise really constituted the gospel (Gal 3:8, 16; John 8:56). All believers, by being in Christ, become heirs of the promise (Gal 3:29; 1 Cor 3:21-23). Not..through the law: That is not as a result of Abraham’s keeping the law. Righteousness of faith: Righteousness received from God by faith (1:17). Those who are outside of the law: If only those who perfectly keep the law-an impossibility-receive the promise, faith has no value. Promise.. of no effect: Making a promise contingent on an impossible condition nullifies the promise (v.13). Law brings about wrath: By exposing man’s sinfulness (7:7-11; Gal 3:19,24).
The promise to Abraham was not through circumcision (vv.9-12) nor through the law (vv.13-16), but through the righteousness of faith. Heir of the world means that Abraham and his seed, in particular Christ, will inherit the earth, a promise that will be fulfilled in the kingdom to be established when Christ returns.
This verse is important in understanding the logic of Paul’s argument and of his view of the Law. Paul basically believes that the existence of the Law turns sin into transgression which would be a willful violation of a known Law. One is thus all the more accountable but most importantly the wrath of God ensues. This is not to say that God does not express his wrath against sin that is not transgression as in 1:18-32 has made evident. The point is that the Law there are even more accountable and a risk of even greater wrath.
Romans 4:16, “16Therefore it is of faith that it might be according to grace, so that the promise might be sure to all the seed, 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. Romans 4:17, “17(as it is written, "I have made you a father of many nations"[d]) in the presence of Him whom he believed--God, who gives life to the dead and calls those things which do not exist as though they did;” Romans 4:18, “18who, contrary to hope, in hope believed, so that he became the father of many nations, according to what was spoken, "So shall your descendants be."[e]”
Paul here is linking together grace, faith and the promise by explaining that God did things as he did so that the promise be secure or reliable, both for those who are linked to Abraham by faith alone (Gentiles) and for those linked to him by circumcision and “works of the Law” as well as by faith. The promises not been based on the law, then only those who did works of the Law could inherit it. The promises; however are based on grace appropriated through faith so everyone can inherit it. Paul then relies upon Gen 17:5 and 15:5 to support his case from the outset that Abraham was meant to be the forefather not only of the Jews but also of the Gentiles. Dunn points out, “God’s gracious outreach to man is of such a character that it can only be received in unconditional openness (J.D.G. Dunn, Romans 1-8, Word Biblical Commentary (Dallas: Word, 1988), p.215).