John Calvin Commentary Acts 19:1

"And it came to pass, that, while Apollos was at Corinth, Paul having passed through the upper country came to Ephesus, and found certain disciples:" — Acts 19:1 (ASV)

Luke shows here that the Church of Ephesus was not only confirmed and increased by Paul’s return, but also that a miracle was performed there, because the visible graces of the Spirit were given to certain uninstructed and new disciples. Furthermore, it is not known whether they were inhabitants of the city or strangers; nor does it greatly matter. Undoubtedly, they were Jews, because they had received the baptism of John; also, it is thought that they lived at Ephesus when Paul found them there.