The doctrine of justification sounds too good to be true and because of that, it raises an obvious problem for us. If it is by God’s free grace that I am declared righteous, then why would I care about my sin? Paul anticipates this argument. Paul begins the argument by the fact that even Peter and himself as good Jews were found to be sinners. Paul uses the word “sinners” as he did back in verse 15  meaning those who lived outside of the law, like the Gentiles. This is the problem the Judaizers had with Peter and Paul they were living like Gentile sinners rather than like the law-abiding Jews they are. This is why the Judaizers accused them of making Jesus a servant of sin. Peter and Paul sought to be justified by faith alone in Jesus which meant they had to give up on the law as a way to get right with God. But does Paul agree with the Judaizers’ claim, no? He says certainly not is Jesus Christ a servant of sin. And Paul argues that it is actually when you try to keep the law in order to be justified that you are sinning. What did he tear down? He tore down the Old Testament law by preaching the gospel of Jesus Christ being crucified and resurrected. So if he went to rebuild that law now, he would then be sinning. It is like what Peter did at Antioch. He tore down the law with his preaching, but then he rebuilt it when he joined the circumcision gang. By rebuilding the law Peter was found to be in sin. 

Paul ends with a shocking statement for a former Pharisee to say. He says through the law he died to the law. Paul used to live for the law as a Pharisee, but now that he is a Christian he himself is dead to it. He is no longer under its power. John Calvin puts it this way, “To die to the law is to renounce it and to be freed from its dominion, so that we have no confidence in it and it does not hold us captive under the yoke of slavery.”