The missionary impulse was strong in Antioch. After fasting and praying, the leaders commissioned Saul and Barnabas for a special work: taking the Gospel of Jesus Christ to new lands.
Acts 13 is the beginning of what is known as Paul's first missionary journey. Saul, Barnabas and Mark begin by traveling to the island of Cyprus (Barnabas' home territory) where they adopt the custom of preaching first in the synagogues.
Some interesting things happened in Cyprus. Saul and Barnabas had the opportunity to share the Gospel with the proconsul, a man named Sergius Paulus. It is from that time on that Luke begins referring to Saul as "Paul." (Many people believe that Saul's name was changed to Paul dramatically, perhaps on the road to Damascus or by a calling from the Lord; the reality appears to be that he did it for missionary purposes - to be able to relate, here, to Sergius Paulus and to have a name that was more cosmopolitan and less Jewish-sounding.) Also, when faced with the opposition of Bar-Jesus (literally, "Son of Jesus" - but no, it's not what you're thinking) Paul is able to strike him blind. An interesting choice, considering that Paul himself was struck blind on the road to Damascus.
Paul and Barnabas feel compelled to continue their mission trip to Asia Minor, but Mark had grown homesick and left the team to return to Antioch. (Mark's abandonment of the mission would later become a sharp point of contention between Paul and Barnabas.) As the pair go about their work, they continue to preach first in synagogues. When, as in the case of Pisidian Antioch, their message is rejected by the Jews, they turn to the Gentiles. There they experience a great deal of receptivity as the kingdom of God is opened to non-Jews, setting the stage for large numbers of Gentiles to begin streaming into the Church.