Ephesus] the capital of the Roman province of Asia, and the most important seaport of Asia Minor, was especially renowned for its great temple of Diana (Artemis), which was one of the wonders of the world. St. Paul chose it for a prolonged stay because (like Corinth) it was on the main line of communication between E. and W., and also because it was a great centre of religious pilgrimage: cp. Acts 19:27.
Certain disciples] They must have arrived since Apollos's departure, otherwise Apollos would have instructed them more perfectly.