Paul says he had to confront Peter “when Peter was come to Antioch” (v.11), where Paul went right after the Jerusalem Council (Acts 15:22-35). Peter arrived some time after that, and sat to eat a meal with some Gentile brethren.
Now there was nothing wrong with that. There used to be under the law (Acts 10;28), but God had “shewed” Peter this was no longer the case with that sheet vision in Acts 10.
We know that Peter understood from that vision that he could now eat with Gentiles, for when some Jews challenged him about it, he told them about the vision and how the Spirit had fallen on the Gentiles (Acts 11:2-15).
So the problem wasn’t that Peter was eating with Gentiles. The problem was that he stopped, because in so doing he was going back to the law instead of recognizing the dispensational change to Paul’s ministry of grace that God was using Peter to introduce. And the reason Paul is telling the Gala-tians that what Peter did was wrong wasn’t to embarrass Peter. It was because they had gone back to the law as well.
So why did Peter return to the law? Paul says it was because he feared “certain from James,” the leader of the Jewish kingdom church. He knew James didn’t know it was okay to eat with Gentiles, for that’s not what they talked about at the council. That council was convened to decide if Gentiles still needed the law to be saved (Acts 15:1,2). The subject of Jews eating with Gentiles never even came up.
But Peter told James about the sheet vision (Acts 15:7,8). So why didn’t that convince James it was all right to eat with Gentiles as it did Peter? It was because four years before Peter got that vision, he spent 15 days with Paul (Gal.1:18), and Paul explained some things to Peter that helped him construe more from the vision than James was able to deduce.
But Peter’s failure to walk according to the truth caused Barnabas to falter as well (Gal.2:13). “Dissembled” is the verb form of the noun “dissimulation,” and both mean hypocrisy (cf.Josh.7:11). God must hate religious hypocrisy, for the Lord was kind to carnal sinners like the woman in John 8, but He laid into religious hypocrites (Lu.11:44).
And that’s another reason Paul is telling the Galatians about this. You see, once you go back to the law, you have to whitewash your sins (Mt.23:27,28). The Galatians tried to cover up their sins by observing religious days (Gal.4:10).
When Peter quit eating with Gentiles, Paul told him he was compelling the Gentiles to feel they should not eat with Jews. In other words, he was putting them under the law. This angered Paul, but when he settled down, he reasoned with Peter by reminding him that Jews like them weren’t guilty of the carnal sins the Gentiles were known for (Gal. 2:15 cf. I Cor.5:1) but they still needed to be saved (v.16).
They were saved by “the faith of Christ.” Don’t change “of” to “in” like new Bible versions do. That word “faith” here means faithfulness (cf.Rom.3:3). In eternity past, God announced His plan to send His Son to earth to be Israel’s Messiah, and the Lord was faithful to do it. Peter’s faith came in when Paul said he “believed in Jesus Christ.” When he believed Jesus was his Messiah, God saved him (John 20: 31). But Paul was saved by believing “Christ died for our sins” (ICor.15:1-4), something the Lord was also faithful to do. Both men were saved by Christ’s faithfulness. They just had faith in two different things the Lord was faithful to do.
And the reason Paul was telling the Galatians about this was that they had begun to think that they had to be faithful to all the things the law said to do to be saved.
Paul’s rebuke meant he loved Peter (cf. Lev.19:17). So when it happens to you, be like David and be thankful (Ps.141:5).