John Calvin on Acts 19:1

1. Luke showeth here that the Church of Ephesus was not only confirmed and increased by Paul’s return, but also that there was a miracle wrought there, because the visible graces of the Spirit were given to certain rude and new disciples. Furthermore, it is not known whether they were inhabitants of the city or strangers; neither doth it greatly skill. It is not to be doubted but that they were Jews, because they had received the baptism of John; also, it is to be thought that they dwelt at Ephesus when Paul found them there.