Paul Confronts Peter in Antioch
Galatians

What provoked the confrontation? - The Event (Gal )

Peter was probably in Antioch shortly after Paul and Barnabas had returned from their mission trip to Galatia, but before the incident in Acts occurred.
Like Paul, Peter was trying to be all things to all men and he made a practice of eating with the Gentile believers from the church at Antioch. But when messengers from James arrived, they probably told him that his "free" lifestyle in Antioch was hindering the work of Jewish evangelism in Jerusalem. So Peter made the decision to withdraw from fellowship with Gentiles because he did not want to offend the Jews to whom he was commissioned to minister.
When Paul saw this inconsistency in Peter's actions, he confronted Peter face-to-face in public. Even though his motives may have been admirable, Peter was wrong to withdraw from Gentile fellowship.
Paul knew that Peter still held to orthodox doctrine - his beliefs about the gospel were correct. But his practices contradicted what he was believing. This type of inconsistency causes a disconnect between doctrine and practice, and the human mind tends to reconcile the problem by changing doctrine to correspond with the practice. This is what Paul was afraid might happen, so he stood firm for the truths of the faith.

Paul knew that true doctrine would be affected by this inconsistent practice, so he brought everyone back to the center line of doctrine. The very truth of the gospel was at stake!
not straightforward (ortho-podousin) = literally, "not straight-footed," not walking straight, believing one thing but doing another. Peter was actually contradicting the doctrine of the gospel by his practice.
Paul was especially concerned that the Gentiles (to whom he was called) would be confused by this inconsistent practice. The Gentiles could only draw one conclusion: that as long as they remained uncircumcised they were only "second class" Christians. Paul calls this "compelling the Gentiles to live like Jews."
Paul knew that the "wall of partition" between Jews and Gentiles had been broken down by Christ (see Ephesians ), but now Peter was helping to rebuild the division between the two groups in the body of Christ.

Paul begins by addressing Peter (as a Jewish believer who had separated himself), and he includes all of the other Jewish believers who are present.
"We are Jews ... but even we Jews know that a man is not justified by works of the law, so even we Jews have believed in Christ so that we may be justified by faith in Christ."
In effect, Paul is saying, "Even you and I denied the obligation of these ordinances by our act of believing in Jesus Christ." By professing this faith, they had committed themselves to the principle that no one can be justified before God by works of the law.
Paul's definitive statement: "No flesh can be justified by the works of the law!"
When they became aware of Christ's work on their behalf, the Jews who thought they were not sinners (like pagan Gentiles), found that they really were sinners. But those who have been justified by faith in Christ should act in a way that is consistent with their beliefs. They should not attemp to rebuild the things that were never able to justify them before God!
The effect of being justified by faith alone is to make a person dead to the law. Since he is now truly alive, he can really live for God! Justification by faith also brings the indwelling ministry of the Holy Spirit into the life of the believer.
The impact of teaching the necessity of obeying the Jewish Law was to destroy the doctrine of the gospel and to make the death of Christ useless!