Acts 13:9

Then Saul, who also is Paul. This is the first time we find the apostle called Paul. Some, therefore, think it was given him when he converted this proconsul, Sergius Paulus. Others, that Saul being a Hebrew word, the Greeks, or rather the Romans, turned it into Paul. (Witham) — This is the first place in which this apostle is called Paul. He took this name out of respect to the illustrious convert he had made in the person of the proconsul, the governor of the island. (Menochius) — Or, more probably, his former name, by a small change, was modelled into Paulus, which was a sound more adapted to a Roman ear. He begins to bear this name only, when he enters on his mission to the Gentiles. (Calmet)

(4.) Saul (who is here for the first time called Paul) fell upon him for this with a holy indignation. Saul, who is also called Paul, v. 9. Saul was his name as he was a Hebrew, and of the tribe of Benjamin; Paul was his name as he was a citizen of Rome. Hitherto we have had him mostly conversant among the Jews, and therefore called by his Jewish name; but now, when he is sent forth among the Gentiles, he is called by his Roman name, to put somewhat of a reputation upon him in the Roman cities, Paulus being a very common name among them. But some think he was never called Paul till now that he was instrumental in the conversion of Sergius Paulus to the faith of Christ, and that he took the name Paulus as a memorial of this victory obtained by the gospel of Christ, as among the Romans he that had conquered a country took his denomination from it, as Germanicus, Britannicus, Africanus; or rather, Sergius Paulus himself gave him the name Paulus in token of his favour and respect to him, as Vespasian gave his name Flavius to Josephus the Jew. Now of Paul it is said,

Verses 4-13 Satan is in a special manner busy with great men and men in power, to keep them from being religious, for their example will influence many. Saul is here for the first time called Paul, and never after Saul. Saul was his name as he was a Hebrew; Paul was his name as he was a citizen of Rome. Under the direct influence of the Holy Ghost, he gave Elymas his true character, but not in passion. A fulness of deceit and mischief together, make a man indeed a child of the devil. And those who are enemies to the doctrine of Jesus, are enemies to all righteousness; for in it all righteousness is fulfilled. The ways of the Lord Jesus are the only right ways to heaven and happiness. There are many who not only wander from these ways themselves, but set others against these ways. They commonly are so hardened, that they will not cease to do evil. The proconsul was astonished at the force of the doctrine upon his own heart and conscience, and at the power of God by which it was confirmed. The doctrine of Christ astonishes; and the more we know of it, the more reason we shall see to wonder at it. Those who put their hand to the plough and look back, are not fit for the kingdom of God. Those who are not prepared to face opposition, and to endure hardship, are not fitted for the work of the ministry.