In Romans 12:9-21, Paul continues to outline his ethic for the life of the believing community at Rome. This ethic began at the beginning of this chapter with the idea of offering one's body as a living sacrifice and having one's way of life and way of thinking transformed and renewed in accoradance with the new age inaugurated by Jesus Christ. Paul then connected this act of mutual sacrifice to the functioning of the community as a body in which all the members work together and support one another. The importance of the community life is once again at the forefront of the discussion in v. 9-21.
At first glance, the exhortations of v.9-21 appear to be almost a completely random conglomeration of commands. The commands here are various and come in rapid succession. Abhor what is evil! Cling to what is good! Be devoted...be fervent...serve...rejoice...weep...be hospitable....be of the same mind....don't take revenge! Do not be overcome by evil but overcome evil with good! If each of these were taken invidividually, this could quickly become an overwhelming spiritual checklist. Fortunately, Paul probably did not intend this as a checklist but rather as a sampling of his vision for the community at Rome.
This vision can likely be summed up in the very first statement of the passage; love without hypocrisy. The many other commands can be seen as explications of this single command. (In Greek, the verbs of verses 9 - 13 do not actually appear as separate commands. They are participles. This means they can be translated as commands or they can be translated as explaining the original command. So it might read like this: "Let love be without hypocrisy by abhoring what is evil and clinging to what it good, by being devoted to one another in brotherly love....") In other words, being devoted to one another and being fervent and serving and rejoicing are not additional commands to loving without hypocrisy. They are examples of what it means for a community to live a life of love without hypocrisy.
In v. 14-21, we find that this rule applies not only to interactions of those with whom these Christians are already at peace. Rather we are to extend this peace and sacrificial love even to those who curse and persecute; to those who pay out only evil. Paul urges his audience not to take justice into their own hands but to trust in God. He tells them not be overcome by evil but to overcome evil with good. With this final exhortation, as is so often the case, it seems that Paul must have the cross of Christ in mind. Jesus did not attempt to overcome the evil that crucified him with equally vicious and destructive acts (which is usually our reaction when confronted with evil). Instead, he trusted in the Father and ultimately the evil of the crucfixion was overcome with the good of the resurrection. Paul is calling upon the Christians at Rome and the Church today to have the same kind of trust in the Father as we lay down our bodies as living sacrificing believing that God is powerful enough to conquer evil with good.