John Calvin Commentary Acts 13:45

"But when the Jews saw the multitudes, they were filled with jealousy, and contradicted the things which were spoken by Paul, and blasphemed." — Acts 13:45 (ASV)

They were filled. It is nothing new for the rage of the wicked to be inflamed when the light of the gospel is brought somewhat nearer; especially when they see the increase of sound doctrine, they break out with greater violence to resist. And it is uncertain whether Luke means, by the word zeal, that they were moved with a certain wicked anger to oppose Paul and Barnabas, as ambition is the mother of both envy and all contention; or whether he uses zeal to mean the indignation conceived from this, because they lamented that the Gentiles were made equal with the people of God. For they considered this a very unfitting thing, that the holy treasure of doctrine, which was the rightful inheritance of the children, should be, as it were, laid at everyone's feet.

Gainsaying and blaspheming. They were so fiercely set on resisting that they finally broke out into blasphemy. And Satan, for the most part, drives the wicked to such madness that when they are overcome by reasoning and discouraged, they become harder and harder; and knowingly and willingly, they eventually spew out blasphemies against God and the truth. Therefore, we must take all the more care when the truth of God is plainly set before us, lest, if we are carried away with a desire to speak against it, we fall immediately into that precipice.