Galatians 1:20

I assure you before God: Paul swears before God to emphasize that his story about his trip to Jerusalem is true.

Peter and James spent fifteen days discussing Paul's message, which matched theirs. Paul did not get his authority from the Jerusalem church. His role and authority as an apostle was independent of Jerusalem.

Paul learned directly from the Lord and did not consult with any person, not even the other apostles. Paul was independent from the other apostles but still agreed with them (2:1–10).

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.