Question: "When and why was Saul's name changed to Paul?"
Answer: One of the often-thought-of “name changes” in the Bible is that of Saul to Paul. The change is commonly linked to Saul’s conversion on the Damascus Road, when the Lord Jesus commissioned him to take the gospel to the Gentiles (Acts 9:1–19). However, at the time of Saul’s conversion, Jesus still addressed him as “Saul.” Later, Jesus told Ananias to find “Saul” in Damascus and restore his sight. Acts 9 goes on to describe “Saul” as increasing in spiritual strength and understanding of Jesus as the Messiah. So, it was not Jesus who changed his name on the road to Damascus. If it wasn’t Jesus’ doing, how did the change from Saul to Paul happen, and when?
The answer is that Saul’s name was also Paul. The custom of dual names was common in those days. Acts 13:9 describes the apostle as “Saul, who was also called Paul.” From that verse on, Saul is always referred to in Scripture as “Paul.”
Paul was a Jew, born in the Roman city of Tarsus. He was proud of his Jewish heritage, as he describes in Philippians 3:5: “Circumcised on the eighth day, of the race of Israel, of the tribe of Benjamin, a Hebrew of Hebrew parentage, in observance of the law a Pharisee.” So zealous and devout was he that persecuting Christians was the natural way for him to show his devotion. He chose to use his Hebrew name, Saul, until sometime after he began to believe in and preach Christ. After that time, as “the apostle to the Gentiles” (Romans 11:13), he used his Roman name, Paul. It would make sense for Paul to use his Roman name as he traveled farther and farther into the Gentile world.
It is interesting that Paul began using his Roman name on Cyprus when the Roman proconsul on that island was converted (Acts 13:12). This was during Paul’s first missionary journey and involved a high-ranking, idolatrous Gentile coming to faith in Christ. The fact that the proconsul’s name was Sergius Paulus has led some to think that Saul took the name Paulus/Paul as a reminder of this event, but the apostle’s name being the same as the proconsul’s is most likely a coincidence.
Using his Roman name was fitting for the man who proclaimed that he would become “all things to all people,” a Jew to the Jews in order to win the Jews, weak to the weak in order to win the weak, etc., all for the sake of the gospel (1 Corinthians 9:19–23). Adopting his Roman name would allow Paul to approach the Gentiles to whom he was sent and speak to them in their own language, becoming as one of them and setting them at ease. It is also possible that Paul gave up the use of his Hebrew name, Saul, with its regal connotation and chose to use his Roman name, Paul, meaning “little” or “small,” because he desired to became smaller in order to present Christ as greater (cf. John 3:30).
Unlike the changing of Simon’s name to Peter (Matthew 16:18–19), which Jesus did for a specific purpose, there is no reference in the Bible to Jesus’ changing Saul’s name to Paul.