"We are Jews by nature and not sinners from among the Gentiles; nevertheless knowing that a man is not justified by the works of the Law but through faith in Christ Jesus, even we have believed in Christ Jesus, so that we may be justified by faith in Christ and not by the works of the Law; since by the works of the Law no flesh will be justified. But if, while seeking to be justified in Christ, we ourselves have also been found sinners, is Christ then a minister of sin? May it never be! For if I rebuild what I have once destroyed, I prove myself to be a transgressor. For through the Law I died to the Law, so that I might live to God." (Galatians 2:15-19)This scripture, at least for me, is a bit hard to parse and understand. I wish Paul had expounded on it a bit more to help us understand what he was trying to say. It is also unclear to me if this is a continuation of what Paul was saying to Peter or a separate thought to the Galatians. Either way, he is continuing to recount to them this incident with Peter that he, and the Galatians, both remember well.
Paul is not saying that Jews are not sinners, just that they are not sinners like the Gentiles. The term "nature" refers to one's growth from germination to maturity. It refers to their lineage and breading. A Jew grew up with an understanding of God and a since of religion that taught them how to please God and to walk in righteousness. The Gentiles had none of these. The Jew's has a desire for righteousness, the Gentiles had no aversion to sin and no compulsion towards righteousness. The Jews were religious and the gentiles sinners. It was a matter of breading and upbringing.
However, this did not mean that Jews were more righteous than Gentiles. While they had the law, they were still transgressors of the law. They were birthed with many advantages yet, in the end, they proved no better than the Gentiles when it came to being justified before God. With all their attempts to keep the law, they were no better than those who didn't even try. Justification cannot, and never could, come from the Law. In this, Gentile and Jew were alike; they both needed Jesus to be justified.
So if a Jew leaves his law and looks for justification in Christ and finds that there is sin raging within him, has his faith lead him to sin? No! The truth is that sin is already in us whether Jew or Gentile. It's not that Christ has lead us to sin but rather that we finally discovered who we truly are inside. If, when the law is removed, we do the same things that the Gentile's do, then we have proven that sin is really a part of us. We can try and keep it in check with the law but we can never eradicate it by the law. Once the law is gone we will always revert to sin, and sometimes even greater sin once the law is gone. This simply shows us that, even the best of religious people, we are all sinners and transgressors of the law.
To be free from sin, truly free, we must die to the law that we might live to God. We can never find our salvation and righteousness in law, only in faith in Jesus Christ and the salvation that He brings. In seeking righteousness and the freedom of Christ we must never seek to rebuild what we have already destroyed. This includes sin but also our dependence upon the law. Our live in Christ is not found in a return to the law. We have already left behind that pathway, we must press on forward to Christ. We must not rebuild what we have already destroyed, we must go forward. There alone is the pathway to freedom and abundant life.