The passage in Romans that establishes the overall purpose of Paul’s letter is in chapter fifteen, often overlooked because it lies in what we often wrongly call the “Devotional” section (12-16). The passage forms the culmination of the letter’s body, since chapter sixteen consists of greetings.
Romans 15:5-9
May the God who gives endurance and encouragement give you the same attitude of mind toward each other that Messiah Jesus had, so that with one mind and one voice you may glorify the God and Father of our Lord Jesus the Messiah. Accept one another, then, just as Messiah accepted you, in order to bring praise to God. For I tell you that the Messiah has become a servant of the Jews on behalf of God’s truth, so that the promises made to the patriarchs might be confirmed and, moreover, that the Gentiles might glorify God for his mercy. As it is written: …” Then he cites four OT texts in 15:9-12 that foresaw the Gentiles being accepted in the family of God alongside their Jewish brothers. These texts interestingly come from all three of the sections of the Hebrew Bible (Deuteronomy, Isaiah, Psalms).
Yes, the Letter to the Romans clearly states the Gospel, but in a way that Gentiles (1:18-2:16) and Jews (2:17-3:8) will together rejoice in the Messiah (3:9-28).
“Or is God the God of Jews only? Is he not the God of Gentiles also? Yes, of Gentiles too, since there is only one God, who will justify the circumcision by faith and the uncircumcision through the same faith” (3:29-30). Students of Romans have often overlooked the significance of that little “or” (ἢ) that begins v. 29.
Romans 15 really serves as a missionary mandate for Paul’s ministry. 15:14-22 make this clear. He is serving as a priest who is offering up the Gentiles reached through his ministry as an acceptable offering to the Father (15:16). This is the missional basis for his plan to leave the eastern Mediterranean for the western part (Italy and Spain) where many more Gentiles will be reached (15:17-22).
But one last effort to evince that unity with the Jerusalem Jewish center still lies ahead of Paul (15:23-29). Note that his purpose is to present an offering from predominantly Gentile churches! He is seeking to flesh out that spiritual unity he has taught in this very passage. When we read Acts, we realize that it did not turn out exactly how Paul had envisioned, perhaps because the Jerusalem leaders were not as open to the Gentile offering as he had hoped. Nevertheless, after a couple of years Paul DID get to see the Roman believers, and it was even at the Roman government’s expense (Acts 21-28)!
In my opinion, in our effort to read Romans through the lens of Luther and medieval Rome, we often have neglected this purpose of Romans as it is found in chapter 15.