Since you belong to Jesus Christ, you have been called to be holy. The Epistle to the Romans was Paul’s way of introducing himself to the Christian community of Rome. Since Paul was not the founder of this community in Rome, he was not writing to answer any pastoral issues that was arising (as he does in some of his other letters) but rather to “preach” to them about the ramification of the Christ-event in human history. As he tells them in this introductory passage, one of the consequences of the incarnation is that even the Gentiles – a people who had been written out and thought of as unworthy of redemption – had been given a lifeline and a place in the salvific plan of God. Through the grace of baptism and their coming to believe in Jesus Christ, the Gentiles have now become Christ’s possession (they belong to Christ). Christ has adopted them and made them co-heirs with him (cf. Romans 8:17).
The second thing that Paul reminds the Roman Christian community is that by virtue of their belonging to Christ, they have been made holy, that is, set apart for a special purpose. And that purpose is the preaching of the Good News of Jesus Christ. In Jesus Christ, God has reconciled the world to himself, Gentiles and Jews alike. In Jesus Christ, the ancient curse of rebellion has been lifted and all creation has been brought back into obedience. The members of this community, therefore, has the obligation of witnessing to this Good News by their lifestyle. The mission for which God had set apart the children of Israel (who until then had been referred to as the elected nation) has now been extended to those who belong to Christ (the baptized). The Roman community had been given the full rights of sonship that the elected nation had hitherto enjoyed, the foremost being leading holy and unblemished lives.