John Calvin on Acts 13:9

9. And Saul, who was also called Paul. Luke showeth now how God brake the bond wherein the deputy was bound. For seeing that he was too much addicted to the magician, he could not embrace true doctrine as one that was free and at liberty; for the devil keepeth those minds (which he hath entangled) in his slavery after a wonderful and incredible manner, that they cannot see even the most plain truth; but so soon as he was once vanquished, Paul could easily enter in unto the deputy. And mark what Luke saith, that the faith is overthrown when the word of God is resisted. Whence we may gather that faith is so grounded in the word, that without this shore “Fultura,” prop or support. it fainteth at every assault; yea, that it is nothing else but the spiritual building of the word of God.