1 Corinthians 16:8

I will tarry at Ephesus until Pentecost. Viz., because at Ephesus was the famous temple of Diana, and because the chief men of Asia Minor lived there. Hence the Proconsul of Asia Minor resided at Ephesus, and, as Philostratus says (Vita Apollonii, lib. viii.), learning flourished there most; and, therefore, there was a greater harvest for S. Paul, and this was what determined him to stay so long there. Ver. 9. A great door... is opened unto me. A great opportunity of preaching the Gospel and of converting many. So Ambrose.