Galatians 1:18-24 meaning

Throughout this last section of the first chapter, Paul explains to his audience over and over how he did not receive his authority or the gospel from men but from God.

Paul was only with the head apostle Peter (Cephas) for fifteen days and didn't see any other major authorities while in Jerusalem except James, the Lord's brother (who was the head elder of the Jerusalem church). This is key: Paul did not meet with an apostle until at least 3 years after Jesus spoke to him on the road to Damascus. He is establishing for the audience, that his authority as an apostle as well as the gospel message that he was preaching was not given to him by man (not even by the apostles) but by God through divine revelation.

In the next chapter of his letter to the Galatians, Paul rebukes Peter for stumbling into legalism and distorting the gospel. Paul could do this because his authority was not given to him by Peter, nor was he taught the good news from Peter or the other of Jesus' original twelve apostles, or the church elders. The gospel was told to him by God, and no one, not even Peter, could change the good news: that Christ died for our sins to rescue us and was then raised from the dead. All according to God's will. Paul preached God's good news of faith in His son, not in works of the law, for our complete justification before Him.

Even before Paul's ministry began, believing Jews in the churches in Judea which were in Christ were already glorifying God because they had heard of his conversion. The idea that Paul the persecutor, who had been throwing fellow believers in jail and allowing them to be stoned, had now become a fellow believer was incredible. But the believing Jews in Judea had to rejoice based on what they had heard because he was unknown by sight to the churches in Judea which were in Christ. "Judea" refers to the southern part of Israel, which includes the city of Jerusalem. So, clearly Paul's authority could not have come from Judea directly or indirectly. Paul's authority came by revelation directly from Jesus, so his Galatian disciples should not listen to the competing Jewish "authorities."