Albert Barnes on Acts 19:36

Seeing then, etc. Since this is established and admitted. Since no one can call in question the zeal of the Ephesians on this subject, or doubt the sincerity of their belief. And since there can be no danger that this well-established worship is to be destroyed by the efforts of a few evil-disposed Jews, there is no occasion for this tumult.

Be quiet. Be appeased. The same Greek word which is used in Acts 19:35, "had appeased the people."

To do nothing rashly. To do nothing in a heated, inconsiderate manner. There is no occasion for tumult and riot. The whole difficulty can be settled in perfect consistency with the maintenance of order.

(b) "do nothing rashly" Prov 14:29