Acts 13:9 - Matthew Poole's English Annotations on the Holy Bible

It is observable, that St. Luke never before called this great apostle by the name of Paul, and henceforth never calls him by the name of Saul. Though there be no great difference in these names, Saul might be more acceptable to the Jews, amongst whom hitherto he had conversed; and Paul a more pleasing name unto the Gentiles, unto whom he was now sent, and with whom for the future he should most converse. He was called Saul as he was a Jew born, a Hebrew of the Hebrews; and Paul, as he was a denizen of Rome; the Romans having that name in good account in several of their chief families. Filled with the Holy Ghost; zeal for God's glory, and faith and power to work the ensuing miracle.