John Calvin Commentary Acts 19:10

"And this continued for the space of two years; so that all they that dwelt in Asia heard the word of the Lord, both Jews and Greeks." — Acts 19:10 (ASV)

All which dwelt. Luke does not mean that the people of Asia came there to hear Paul, but rather that the fragrance of his preaching spread throughout all Asia, and that the seed was sown far and wide. Thus, his labor was fruitful not only for one city but also for distant places.

Indeed, it often happens that when the truth of God is preached in one place, its message is heard even where the minister's own voice does not carry, as it spreads far and wide. This occurs because the message is passed from person to person, with one teaching another. For one person would not be sufficient unless everyone were diligent in spreading the faith themselves.