Galatians 1:18 Then after three years I went up to Jerusalem to see Peter, and abode with him fifteen days.
19 But other of the apostles saw I none, save James the Lord’s brother.
20 Now the things which I write unto you, behold, before God, I lie not.
Now we see that Paul is going to Jerusalem to meet with Peter because he was the head of the Christian movement at this time. He did not go to meet with Peter to learn from him but to let him know he was ready to preach the gospel to the Jews as well as the gentiles. He stayed with Peter for 15 days to let him see that the Holy Spirit had enabled him to preach the true Gospel. Paul did not meet with any others but James the brother of Jesus. James also was the leader of the church in Jerusalem. The Jewish legalists were saying Paul was a liar and so Paul was there to show them that what he had came from the Holy Spirit. Sometimes we have people who doubt if we are the righteous person we say we are. So we need to know that we have to defend what we stand for sometimes. We should always have enough of the Word of God in us to be able to show people the truth about what we believe.