We don't know how much time passed between Paul's visit to Jerusalem and Peter's visit to Antioch, but it seems much has changed. When Paul left Jerusalem it seemed he and Peter were in complete agreement but now they are at odds. Verse 11 says...
11 But when Cephas came to Antioch, I opposed him to his face because he stood condemned.
What Paul means is that Peter "was clearly in the wrong" and there was no way to avoid a confrontation.
The issue was Peter had changed his eating habits. Verse 12...
12 For he regularly ate with the Gentiles before certain men came from James. However, when they came, he withdrew and separated himself, because he feared those from the circumcision party.
Who you choose to eat with may not seem like a big deal but there's more going on than just that.
It's worse than Peter just not wanting to fellowship with Gentiles because Peter himself had been living like a Gentile. He had accepted Paul's teaching and but when his Jewish friends showed up, for appearances sake, he withdrew and separated himself.
The circumcision party were those that kept the Jewish ceremonial laws. These laws were supposed to make you "clean" or religiously acceptable.
You couldn't touch dead things (Numbers 19:11-13). Women who gave birth were unclean (Lev 12:1-8). You couldn't eat "unclean" animals like pigs and camels. You couldn't keep the Passover if you were unclean (Num 9:6).
The ceremonial laws were designed to teach that sinful people couldn't approach God without first being cleansed and they had to avoid others, too until they went through the purification rites and waited a period of time.
But Peter knew the time for these ceremonial laws was past.
Peter heard Jesus when he said in Mark 7:14-15
"...Listen to me, all of you, and understand: Nothing that goes into a person from outside can defile him but the things that come out of a person are what defile him.”
Peter had a vision of unclean animals and in Acts 11:7-9 he
"...heard a voice telling me, ‘Get up, Peter; kill and eat.’"
Peter got the message. Acts 10:34-35 says, Peter began to speak:
“Now I truly understand that God doesn’t show favoritism, but in every nation the person who fears him and does what is right is acceptable to him."
That's why he was such a hypocrite and his hypocrisy was effecting others. Verse 13...
13 Then the rest of the Jews joined his hypocrisy, so that even Barnabas was led astray by their hypocrisy.
Peter knew how he should be treating the Gentiles but when his circumcised buddies came around he showed what he really thought of them. This is the worst kind of sin. When it was only the Gentiles he was friendly but when his buddies came around he joined in with ridiculing them, even Barnabas did.
Peter was a hypocrite but it goes even worse than that. Verse 14...
14 But when I saw that they were deviating from the truth of the gospel, I told Cephas in front of everyone, “If you, who are a Jew, live like a Gentile and not like a Jew, how can you compel Gentiles to live like Jews?”
What's worse is that Peter was deviating from the truth of the gospel. The gospel was going in one direction and he was going in another because he wasn't living it out. He was deviating from the truth that we are all sinful people unable to save ourselves, in need of complete and total rescue. He was acting like the Jews were better than the Gentiles even though intellectually he knew they weren't.
Peter wasn't living out the implications of the gospel. He understood the gospel, even preached it, but he wasn't living by it.
His sin was basically nationalism which is a form of legalism. Nationalism insists that in order to be pleasing to God you need to be of a certain nation. It's a type of legalism because it adds to the gospel truth of "Christ alone." Nationalism is what happens when individuals and churches fail to live out the implications of the gospel.
Churches fail to live out the gospel when they emphasize their distinctions more than the gospel. Presbyterians do this when the form of government becomes the most important thing. Baptists do this when baptism becomes the most important thing. Seventh Day Adventists do this when the Sabbath day becomes the most important thing. Our distinctions may be important but they are not the gospel.
Individual Christians can fail to live out the gospel, too. Working class Christians may not like wealthy Christians and vice versa. Talented Christians may have little patience with the untalented. The elderly can't tolerate the young. The young can't tolerate the elderly. Those that are socially awkward don't like being around the socially polished.
Now, we may be polite with others on the surface. We may say we accept all people, even sit next to them at church. But we show our hearts when we don't really make any effort to know them. We show our true colors when we make fun of them behind their backs with others who think like we do.
This kind of behavior is not in line with the gospel. The gospel tells us we are all unclean without Him and clean with Him. We are neither Jew nor Gentile but one in Christ. In verse 15 Paul makes this argument with Peter...
15 We are Jews by birth and not “Gentile sinners,” 16 and yet because we know that a person is not justified by the works of the law but by faith in Jesus Christ, even we ourselves have believed in Christ Jesus. This was so that we might be justified by faith in Christ and not by the works of the law, because by the works of the law no human being will be justified.
"Gentile sinners" is in quotes because you could just as easily say "Jewish sinners." We are all sinners who need to be justified.
"Justified" is a legal term that means essentially the same thing as "cleansed." We are made clean not by the works fo the law but by faith in Jesus Christ. This is as true for Jews as it is for Gentiles. There's no difference. No one is justified apart from belief in Christ Jesus. Keeping the law, not keeping the law, makes no difference when it comes to being declared legally righteous which is also what "justified" means.
J.I. Packer says this:
“To ‘justify’ in the Bible means … to declare … of a man on trial, that he is not liable to any penalty, but is entitled to all the privileges due to those who have kept the law. Justifying is the act of a judge pronouncing the opposite sentence to condemnation—that of acquittal and legal immunity.”
The gospel cuts through works and makes them of no effect. Jews are fully justified by faith in Christ and so are Gentiles.
But apart from the gospel our only option is to compare ourselves, our group, our nation with others and make those comparative differences the basis for our justification. Without realizing it, that's what Peter was doing.
Peter was being a racist which is essentially works-righteousness. It's trying to improve your own standing by declaring your race is better than another. I'm not speaking politically, but biblically. Racism, in the biblical sense, is forgetting (or not knowing in the first place) that we are saved by grace and then attempting to justify yourself by your nationality.
It's understandable that there would be racial prejudice in a world without Christ, but the gospel should cut through it all. Racism, nationalism, prejudice, shouldn't be in the church. This is what Paul is trying to address but notice he goes about it in a gentle way.
He doesn't attack Peter and tell him to change his ways, or else. He goes to the heart of the matter, which is that Peter had forgotten the gospel and wasn't applying it. He needed to be reminded as we all do.
Peter was loved by God, not on the basis of his righteousness, but on the basis of Christ's. Peter needed to be reassured of his acceptance in Christ. He was afraid of what others might think more than what God thought. He had forgotten that the gospel casts out fear and is the greatest motivator to love others as Christ loves us, unconditionally.
In verse 17 Paul tried to reason with Peter...
17 But if we ourselves are also found to be “sinners” while seeking to be justified by Christ, is Christ then a promoter of sin? Absolutely not! 18 If I rebuild those things that I tore down, I show myself to be a lawbreaker.
The language in verse 17 and 18 is a little obscure but the basic meaning is this, "If someone who knows they are justified by faith sins, is it because justification-by-faith-in-Christ promotes sin? Not at all! But if someone who professes faith in Christ keeps on with the same sinful lifestyle, rebuilding the sinfulness that Christ died to destroy the penalty for, making no effort to change, then it proves that this person never really grasped the gospel, but was just looking for an excuse to live in disobedience to God."
Paul knows Peter isn't trying to use the law as an excuse to sin but Peter needed to be reminded of how to live according to the gospel. Verse 19 shows how a person in Christ ought to live...
19 For through the law I died to the law, so that I might live for God.
Before Paul and Peter became Christians, even the good things they did, were done for themselves. They are dead to that way of living. Now that they are in Christ they have a different motivation and purpose. They live for God.
In other words, "The law itself showed me that I could never make myself acceptable through it. So I stopped “living to it”. I died to it as my savior. Though I obeyed God before, it was simply to get something from Him; it was for my own sake. Now I obey Him simply to please Him. I now live for Him."
Peter needed to be reminded that this is the way to live. So do we. Now, notice the tension of living this way in verse 20:
20 I have been crucified with Christ, and I no longer live, but Christ lives in me. The life I now live in the body, I live by faith in the Son of God, who loved me and gave himself for me.
On one hand Paul is dead but on the other he lives. There's tension. He is dead to selfish motivations but alive to godly ones. He lives to please God and not himself. This is how we live out the gospel in daily life.
We live it out knowing my past is Christ's past. Knowing, that because Christ has no condemnation, neither do I. And because Christ is loved, I am loved, and Christ lives in me!
But this isn't to say that we just sit back and do nothing once we are saved. Verse 21...
21 I do not set aside the grace of God, for if righteousness comes through the law, then Christ died for nothing.
In other words, "Now when I live my life and make my choices and do my work, I do so remembering who I am by faith in Christ, who loved me so much, and still does!" I do not set aside the grace of God, I live by grace!
Only when we understand how much we are completely loved and made righteous in Christ will we have the motivation to joyfully repent and cast aside our feelings of racial and national superiority. Only when we apply the gospel to our daily living will we be free to love others the way we've been loved.
We continue to live as Christians the way we started as Christians, by grace. It was by grace we we saved. We did nothing to earn it. So we continue to live by grace with ourselves and with others. To live any other way is hypocritical at best and at worst makes Christ's death meaningless.
"Imagine that your house were burning down but your whole family had escaped, and I said to you: Let me show you how much I love you! and ran into the house and died. What a tragic and pointless waste of a life, you would probably think. But now imagine that your house was on fire and one of your children was still in there, and I said to you: Let me show you how much I love you!, ran into the flames, and saved your child but perished myself. You would think: Look at how much that man loved us."
If we could save ourselves then Christ died for nothing. When we add to what Christ did, requiring this or that of ourselves or of others, we make a mockery of Christ's work on the Cross. We treat Christ's death as if it had no effect.
But Christ's death did accomplish something for those that believe in Him. Christ's death is the guarantee of our salvation and it means everything to us. And it teaches us how to go on living for him, serving him, not trying to repay him, but in an earnest attempt to please Him.
This is how we live out the gospel. Peter needed to be reminded of this way of life and may we not be too proud to admit that we need reminded too.