Would you draw a connection between who you had round for dinner and whether or not you really believed the Gospel? Paul did.
A look at the text: Read Galatians 2:11-14
When Paul had visited Jerusalem, he had found himself in agreement with Peter but at a later date, Peter had reason to visit the Antioch church and this time things are not as amicable. Paul says that he opposed Peter, face to face. Notice that he doesn’t seek to compromise with or appease Peter, he doesn’t grumble behind his back either. He is straight with him. This is because Peter “stood condemned.” Peter was in the wrong but the language seems even stronger than that, he is judged, he is found to be acting unrighteously in God’s eyes, though notice that later there is the suggestion that Peter in effect condemned himself (v11).
The cause of the dispute was that when Peter first arrived in Antioch, he had happily eaten with both Jewish (circumcised) and Gentile (uncircumcised) believers alike. Then more people had come from the Jerusalem church. We know two key things about them. They were linked to James, though James may not have held the same view himself and they were from the circumcised. This seems to have been a party within the church that was encouraging Gentile believers to receive circumcision. Peter was afraid of them and so withdrew from fellowship with others (v12). Other Jewish believers, including Barnabas got drawn into the same behaviour which Paul considers hypocritical (v13).
Paul will not accept this, he considers it hypocrisy. Peter and other Jewish believers had welcomed the freedom that the Gospel brought including freedom from certain laws such as the kosher rules. Peter was in effect choosing a Gentile/uncircumcised lifestyle whilst denying this possibility to Gentile believers. He was imposing a level of law and restriction on them which he had discarded for himself (v14).
Digging Deeper
Paul sees Peter’s actions as significant and uses the language of condemnation to make this clear. The Galatians may have been tempted to see issues such as circumcision and table fellowship as “second order” issues but Paul establishes a direct link between who you will share fellowship with and the Gospel, just as he links attitude to secondary external rituals to the Gospel.
This is because refusing to sit and eat food with someone for a Jew meant to treat them as unclean. In effect, Peter was treating uncircumcised believers as outside of God’s covenant people, as unbelievers. This amounted to a form of unsanctioned church discipline. So it was the actions of Peter and the Judaizers that brought these two issues of circumcision and table fellowship into the sphere of first order Gospel issues. They became Gospel issues because by refusing to accept people who weren’t circumcised, by treating them as outsiders, they were in effect saying that the Gospel had been ineffective, that those Gentiles were not yet truly saved.
A look at ourselves
The challenge for us then is that our ethics, how we choose to live our lives tell us something about our doctrine, what we believe. In other words, what you believe affects how you live and how you live affects what you believe.
We are not saved by our good works but we are saved for good works. This means that how we live our lives, our love and concern for others, our care for those in need, our ability to welcome, our readiness to forgive demonstrate whether or not we have grasped the Gospel. Indeed, the heart attitude that these actions show is more important than the external show of religious ritual.