Acts 19:1

Here is presented by Luke the story of certain Christians who needed re-baptism (Acts 19:1-7), a record of Paul's mighty successes in Ephesus (Acts 19:8-13), the account of the exorcists who were exorcised (Acts 19:14-20), a summary of Paul's further work in Asia (Acts 19:21-22), and a full account of the uproar created by Demetrius and the shrine-makers (Acts 19:23-41).

CHRISTIANS WHO NEEDED TO BE RE-BAPTIZED

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)

While Apollos was at Corinth ... definitely suggests that these disciples were converts made by Apollos; and that the providence of God appears in this: that, whereas Aquila and Priscilla had taught Apollos the way of the Lord more accurately, some of those whom he had inadequately instructed were found and properly taught by Paul. Aquila and Priscilla had sent Apollos on to Corinth.

Certain disciples ... That these men were Christians is certainly to be inferred from the way in which Luke describes them as `disciples.'[1]

Through the upper country ... This was the country north of Ephesus.