Galatians 2:12

• Peter ate with the non-Jewish believers because God had shown him it was right (Acts 10:9–16, 34–35).

• James's friends wanted to stop Jewish and non-Jewish believers from eating and meeting together freely. These people insisted that everyone should follow strict Jewish religious customs. They tried to force non-Jewish believers to follow Jewish rules about food and religious practices.

• he used to eat with the Gentiles. But when they arrived, he began to draw back and separate himself: When Peter refused to share meals and the Lord’s Supper (see 1 Corinthians 11:20–22, 33–34) with fellow Christians, he created a divide between Jewish and Gentile (non-Jewish) Christians. This suggested that Jewish customs made them more acceptable to God. If not uncorrected, Peter’s actions would have weakened the message of salvation by grace through faith.

• for fear of those in the circumcision group: James's friends pressured Peter so much that he became afraid. This was surprising because earlier, when people criticized Peter for the same thing, he had stood up to them bravely and spoke strong words to defend his actions (Acts 11:2–18).
  
  Peter might have had two reasons for his actions. First, he might have worried that his actions would make it harder for Jewish people to accept Jesus. Second, he might have been worried about the safety of Jewish Christians in Judea, who were being treated badly by non-Christian Jews (compare 5:11; 6:12). But even if Peter had good reasons, what he did was still wrong.

In Antioch, Peter and others went against their own beliefs and changed the good news about Jesus. This event is not mentioned in the book of Acts. Paul corrected Peter, showing that Paul's role as an apostle was independent of Jerusalem and true to the good news about Jesus.

The Judaizers (people who insisted on following Jewish customs) came to Galatia. They preached that both faith and circumcision were necessary. They questioned Paul's authority as an apostle and tried to discredit his message. Paul defended his authority by showing that past events proved his message was the true good news.

Some people were against Paul and questioned whether he was a true apostle. They did not believe he was honest and did not think he had the right to be a leader in the church. So Paul begins his letter by explaining that he really was an apostle with authority from God.