The Ministry of Apollos in Ephesus. He Is Instructed In The Way of the Lord (18:24-26).
Meanwhile there arrived in the west of Asia Minor, in Ephesus, which Paul had visited but had not yet really evangelised, ‘a certain Jew named Apollos'. This remarkable person proclaimed the baptism of John, and the Coming One whom John had promised and to Whom he had pointed. He knew about Jesus, and believed, but his knowledge was incomplete. He was ‘instructed in the way of the Lord' (compare Luke 3:4) and ‘taught diligently (or accurately) the things concerning Jesus'. Here ‘Lord' may mean the God Whom John served, or the Coming One to Whom John had pointed. But either way it was not a full faith in the crucified and resurrected Jesus. He had to be taught ‘the way of God' more perfectly.
But once he had been taught the way of God more accurately he began to proclaim the Messiah as Jesus along with all that went with it. A major explanation for the introduction of Apollos' ministry is that it was in order to confirm that once Paul was prevented from engaging in further missionary journeys there was another who would take his place. It may well be that Ephesus first, and then Corinth, was a deliberate reversal of Paul's path, which had been Corinth first and then Ephesus, in order to demonstrate that he was taking on Paul's ministry (compare the reversal of visits to places when Elisha takes over from Elijah - 2 Kings 2). But it is also an essential first step in Luke's re-enactment of the triumph of God from John the Baptiser to the final defeat of Satan at the cross, as suggested above.
We must pause here to remind ourselves of the importance of Ephesus in the ongoing of the Good News. It was the major city of western Asia Minor, itself an area of great cities, and was the third largest in the empire (although being on the wane due to difficulties in preventing the silting up of its harbour), containing over 250,000 inhabitants. Being at the end of the Asiatic caravan route, and a natural landing point from Rome, it was a prominent harbour. With its theatre (capacity 25,000), baths, library, agora and paved streets together with its huge and world-famed temple of the many-breasted Diana (Greek: Artemis) and its three temples dedicated to emperor worship it saw itself, and was seen by others, as an important centre of civilisation and religion. It had a large colony of Jews who enjoyed a privileged position under Roman rule. It would be an important centre for the spread of the Good News throughout the Roman province of Asia.