But when Cephas came to Antioch I opposed him to his face, because he stood condemned. For before certain men came from James, he ate with the Gentiles; but when they came he drew back and separated himself, fearing the circumcision party. And with him the rest of the Jews acted insincerely, so that even Barnabas was carried away by their insincerity. But when I saw that they were not straightforward about 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, who are Jews by birth and not Gentile sinners, yet who know that a man is not justified[a] by works of the law but through faith in Jesus Christ, even we have believed in Christ Jesus, in order to be justified by faith in Christ, and not by works of the law, because by works of the law shall no one be justified. But if, in our endeavor to be justified in Christ, we ourselves were found to be sinners, is Christ then an agent of sin? Certainly not! But if I build up again those things which I tore down, then I prove myself a transgressor. For I through the law died to the law, that I might live to God. I have been crucified with Christ; it is no longer I who live, but 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 were through the law, then Christ died to no purpose.
–Galatians 2:11-21