Albert Barnes' Notes on the Whole Bible - Acts 18:18
And sailed thence into Syria - Or set sail for Syria. His design was to go to Jerusalem to the festival which was soon to occur, Acts 18:21.Having shorn his head - Many interpreters have supposed that this refers to Aquila, and not to Paul. But the connection evidently requires us to understand it of Paul, though the Greek construction does not with certainty determine to which it refers. The Vulgate refers it to Aquila, the Syriac to Paul.In Cenchrea - Cenchrea was the eastern port of Corinth.... read more
The Pulpit Commentary - Acts 18:18-23
Retrospect. An interval in Paul's labors; how long cannot be known. Probably a needed rest; possibly connected with a vow. Employed in visiting Ephesus, sailing to Caesarea, his long fellowship with the Church there, repairing to Antioch and recounting his successes, for some time; and then revisiting the scene of his labors in Galatia and Phrygia. Thus it was a time of comparative bodily rest, of reflection and preparation for the future, and of confirmed intercourse and fellowship with... read more