John Calvin Commentary Acts 21:30

"And all the city was moved, and the people ran together; and they laid hold on Paul, and dragged him out of the temple: and straightway the doors were shut." — Acts 21:30 (ASV)

And the city was moved. Here we see the fickleness of the common people, who consider Paul a condemned man before they even hear him.

It is indeed no surprise when the city is stirred up about godliness; but this particular agitation is an instance of perverse zeal and mad rashness, in that they set themselves against Paul before they know his case. For in this corruption of nature, perversity is joined with foolishness, so that those who can hardly be moved by many exhortations to do well will readily, of their own accord, hasten to maintain an evil cause.

It is a difficult situation that the whole world should suddenly be armed against us through the persuasion of a few. But since it pleases the Lord that it should be so, let every one of us prepare himself by this and similar examples to suffer all kinds of assaults, and to bear and endure all onslaughts.