Acts 13: the first mission trip

The church in Antioch was gathering different kinds of people: Barnabas - a levite Jews, Simon from Africa and Manaen who was raised together (syntrophos) with Herod Antipas (he should be rich). For outsiders, they were the Cristianos - people of Christ. They were strangely together because of Christ, that's why they called some attention from outsiders. The Holy Spirit spoke to send Saul and Barnabas to a mission. 
In Paphos they were requested by the proconsul Sergius Paulus because he wanted to analyze the gospel. Why? Perhaps, due to some disagreements when Saul and Barnabas preached there. The proconsul was assisted by a magician called Bar Jesus  who was against the gospel and was disturbing when Barnabas and Saul was preaching to the proconsul. Saul said:

9 But Saul, who was also known as Paul, filled with the Holy Spirit, stared at him, 10 and said, “You who are full of all deceit and fraud, you son of the devil, you enemy of all righteousness, will you not stop making crooked the straight ways of the Lord? 11 Now, behold, the hand of the Lord is upon you, and you will be blind and not see the sun for a time.” And immediately a mist and a darkness fell upon him, and he went about seeking those who would lead him by the hand. 

This event led the proconsul to believe in the gospel. Perhaps, Saul (Jewish name) began to use the name Paul (Roman name) as a way to be associated to Sergius Paulus .

The family of Sergius Paulus  was very influential in Pisidian Antioch. They went there (perhaps to a recommendation from the proconsul). There, Paul preaches:

MSG: 36-39 “David, of course, having completed the work God set out for him, has been in the grave, dust and ashes, a long time now. But the One God raised up—no dust and ashes for him! I want you to know, my very dear friends, that it is on account of this resurrected Jesus that the forgiveness of your sins can be promised. He accomplishes, in those who believe, everything that the Law of Moses could never make good on. But everyone who believes in this raised-up Jesus is declared good and right and whole before God.

Paul says in the synagogue that Jesus is the One to make us whole before God, and this can't be accomplished by the Mosaic Law. Thus, imagine the reaction of this message among the Jews!