In his epistle (letter) to the Church in Galatians, St. Paul writes,
But knowing that a man is not justified by works of the Law, but through faith in Jesus Christ. And we believed in Christ Jesus, in order that we might be justified by faith in Christ and not by works of the Law, because by works of the Law no flesh is justified (Gal 2: 16).
Here, St. Paul writes of the Mosaic Law — the Law given to Moses by God in the Sinai wilderness. This Law helped define the Jewish people, and set them apart from their Gentile counterparts. However, through much of his ministry St. Paul battled the Judaizers. These were Jews who came to faith in Christ, but insisted Gentile converts to Christ become subject to the Mosaic Law, chiefly circumcision. In brief, St. Paul countered their argument by stating, “if you Jews cannot keep the Law, why do you want to impose it upon Gentiles?”