Matthew Poole and continuators on Acts 21:22

22 What is it therefore? the multitude must needs come together: for they will hear that thou art come.

It can't be otherwise; or what else remains to be done?

All the faithful must meet; for the Magistrate then being Pagan, and enemies both to the Church and the Gospel; in matters of great moment, especially when there was any fear of a Schism, the whole multitude of Believers were gathered together to consult about it.