Galatians 2:11-21 NRSV
But when Cephas came to Antioch, I opposed him to his face, because he stood self-condemned; for until certain people came from James, he used to eat with the Gentiles. But after they came, he drew back and kept himself separate for fear of the circumcision faction. And the other Jews joined him in this hypocrisy, so that even Barnabas was led astray by their hypocrisy. But when I saw that they were not acting consistently with the truth of the gospel, I said to Cephas before them all, “If you, though a Jew, live like a Gentile and not like a Jew, how can you compel the Gentiles to live like Jews?”
We ourselves are Jews by birth and not Gentile sinners; yet we know that a person is justified not by the works of the law but through faith in Jesus Christ. And we have come to believe in Christ Jesus, so that we might be justified by faith in Christ, and not by doing the works of the law, because no one will be justified by the works of the law. But if, in our effort to be justified in Christ, we ourselves have been found to be sinners, is Christ then a servant of sin? Certainly not! But if I build up again the very things that I once tore down, then I demonstrate that I am a transgressor. For through the law I died to the law, so that I might live to God. I have been crucified with Christ; and it is no longer I who live, but it is Christ who lives in me. And the life I now live in the flesh I live by faith in the Son of God, who loved me and gave himself for me. I do not nullify the grace of God; for if justification comes through the law, then Christ died for nothing.
NRSV: New Revised Standard Version