Acts 18:21

I must . . . keep this feast--probably Pentecost, presenting a noble opportunity of preaching the Gospel. but I will return--the fulfilment of which promise is recorded in Act 19:1.

In this chapter we have, I. Paul's coming to Corinth, his private converse with Aquila and Priscilla, and his public reasonings with the Jews, from whom, when they rejected him, he turned to the Gentiles (Act 18:1-6). II. The great success of his ministry there, and the encouragement Christ gave him in a vision to continue his labours there, in hopes of further success (Act 18:7-11). III. The molestations which after some time he met with there from the Jews, which he got pretty well through by the coldness of Gallio, the Roman governor, in the cause (Act 18:12-17). IV. The progress Paul made through many countries, after he had continued long at Corinth, for the edifying and watering of the churches which he had founded and planted, in which circuit he made a short visit to Jerusalem (Act 18:18-23). V. An account of Apollo's improvement in knowledge, and of his usefulness in the church (Act 18:24-28).

18:21 “I will come back later”: Paul later spent significant time in Ephesus during his third missionary journey (19:1–20:1; see 19:8, 10).