Without doubt Ephesus was the most important of all the cities in which Paul labored. It was not only the capital of the province of Asia but, being the site of the famous temple of Diana, it was the religious center of the empire.
Every year tens of thousands of pilgrims visited the city. Indeed, the merchants derived much of their wealth from the tourist trade (Acts 19:25-27). So important was Ephesus that Paul remained there for the best part of three years (Acts 20:31), longer than in any other city. On his departure he left Timothy in charge of the work (1 Tim 1:3). Priscilla, Aquila, and Apollos all labored in Ephesus (Acts 18:24-26).
Later on the apostle John took up residence there. In the Acts of the Apostles Luke records four major addresses given by Paul. One of these was his farewell address to the elders of the church in Ephesus (Acts 20), which affords valuable insights into his missionary methods. Paul spent the first three months in Ephesus preaching in the synagogue, “arguing and pleading about the kingdom of God” (Acts 19:8). When opposition drove him from the synagogue he moved to the hall of Tyrannus, where he carried on a daily dialogue with all who would listen.
Some idea of the effectiveness of Paul’s ministry there can be seen from Luke’s comment: “This continued for two years so that all the residents of Asia heard the word of the Lord, both Jews and Greeks ’ (Acts 19:10).
This is one of the most remarkable statements in the book of Acts. It shows clearly the enormous influence that Paul was able to exercise when situated in a strategic center. When Luke says that “all the residents of Asia heard the word of the Lord,” we need not assume that it refers only to a widespread sowing of the seed with no concerted effort to secure a harvest.
We know from Revelation 2 and 3 that later on there were seven well-established churches in the province of Asia, each one identified by name. How, when, and by whom were they founded? Is it not reasonable to suppose that they were the result of Paul’s three-year stay in the capital?
J. Herbert Kane, Christian Missions in Biblical Perspective