John Calvin on Acts 19:20

20. Grew mightily [lions.] The word κατα κρατος doth signify that the word increased not a little, (or that these proceedings were not common) as if he should say, that in those increasings appeared rare efficacy, and such as was greater than it used commonly to be. The word grew do I refer unto the number of men, as if he should have said, that the Church was increased, new disciples being gathered together dally, because doctrine is spread abroad. And I interpret that, that the word was confirmed in every one thus, to wit, that they did profit in the obedience of the gospel and in godliness more and more, and that their faith took deeper root.