Paul’s First Post-Conversion Trip to Jerusalem (the 1st of 5):
Around A.D. 40 (“three years after his conversion”) Paul traveled to Jerusalem where he connected with Barnabas who introduced Paul to the apostles James, the brother of Jesus and Simon Peter (Acts 9:26-30 & Gal 1:13-24). Many think that Paul already knew Barnabas, and that they may have been fellow students at Rabbi Gamaliel’s Hebrew law school in Jerusalem (a school for training Pharisees). Around A.D. 44 Paul traveled to Jerusalem again to take financial aid from the Antioch Christians to Jerusalem (that was Paul’s 2nd post-conversion trip to Jerusalem).
Antioch is the first place that the members of the Jewish “sect of the Nazarene” were called “Christians” (Acts 11:26).
Lange's Christian Chronicle 