We have spent a long time with Paul in Corinth in the last few chapters – appropriately, since Paul spent a long time there, a year and a half according to Acts 18.11, and perhaps longer (v. 18). But then, according to Acts, he sailed across the Aegean Sea to Ephesus with Priscilla and Aquila. He seems to have stayed there only briefly, since he was headed for Jerusalem and Antioch. Acts refers to him having his hair cut off 'because of a vow he had taken' (18.18). Jews made vows for various purposes, including the giving of thanks for past blessings; such vows typically would have included the shaving of the head and abstinence from alcohol, and would have ended with the offering of a sacrifice in Jerusalem. Acts very briefly describes Paul going to Jerusalem and greeting the church there (18.22). We get the impression that it was a quick visit, which would be understandable, given Paul's history. Then Paul went on to Antioch. How long he stayed there is not clear, but Acts soon has him back on the road, headed for Galatia and Phrygia again, visiting the churches that he and Barnabas had founded.
Acts mentions at this point a man who will be an important player in the story, Apollos (18.24–8). Apollos came from Alexandria in Egypt. Alexandria was one of the Roman Empire's great cities, with a large population of perhaps a million people, including a large Jewish community. It was a centre of learning, boasting a huge and famous library and a research centre called the Museum. It was the place where the famous Greek translation of the Old Testament, the Septuagint, was produced in the three centuries before the time of Christ, and it was also the home city of Philo, a famous Jewish philosopher and writer of the first century AD, who sought to combine the best of Greek and Jewish learning.
Apollos is described in Acts as a 'learned' (logios) man, 'powerful in the Scriptures' (18.24). He had been taught 'the way of the Lord' and about Jesus, and was 'fervent [literally 'boiling'] in spirit'