If I had to pick a single passage of scripture and say that it was my favorite, I would have to say that The High Priestly Prayer in John chapter 17 is that passage. It is my favorite for a number of reasons, but one of those reasons is in it the Lord prayed to the Father on behalf of the church for unity. (cf. John 17:20-23) In the epistle to the church at Ephesus 2:13-16 the apostle calls the Law of commandments the enmity. It is this enmity that divides the Jew and the Gentile. Paul established in Romans 1-3 that both Jew and Gentile are guilty, the Gentile without law and the Jew under the Law have all sinned and fallen short of the glory of God. Therefore, both the Jews and the Gentiles alike are justified through faith in Jesus Christ alone.
J. D. G. Dunn in his Dictionary article “Romans, Letter to the” established three purposes for the apostle Paul in writing the epistle; missionary, apologetic and pastoral.1 With regards to Pastoral he said that Paul wrote to heal both a potential and real problem within the church in Rome.2 That problem was the enmity previously mentioned. Therefore, since Paul had established that both Jew and Gentile are under sin, and that Jew and Gentile are both Justified as a gift, by the grace of God, through faith in Christ Jesus there was no longer an enmity; therefore, Christian unity was now free to abound.
In Romans 12:1-2 he is telling the whole church both Jew and Gentile to give of themselves, and that their thinking about the way they saw the world is to be changed. By saying to give your bodies as a living sacrifice he was telling them to die to self. So then in chapter 15 we see what this looks like, in bearing the others weakness and not just pleasing yourself. So then he admonishes them to have one mind coming from the scriptures and not the world. That way the entire church could glorify God in unity. We all in Christ Jesus, Jew and Gentile are to accept one another and bear one another’s burdens. (Romans 15:1-7, cf. Gal 6:1-2)
1 J. D. G. Dunn, “Romans, Letter to the” in Dictionary of Paul and His Letters, eds. Gerald F. Hawthorne, Ralph P. Martin, and Daniel G. Reid (Downers Grove, IL: IVP Academic, 1993), 839-840.