Having tarried after this yet many days (eti prosmeinas hēmeras hikanas). First aorist (constative) active participle of prosmenō, old verb, to remain besides (pros as in 1Ti 1:3) and that idea is expressed also in eti (yet). The accusative is extent of time. On Luke’s frequent use of hikanos See note on Act 8:11. It is not certain that this period of “considerable days” which followed the trial before Gallio is included in the year and six months of Act 18:11or is in addition to it which is most likely. Vindicated as Paul was, there was no reason for haste in leaving, though he usually left after such a crisis was passed.
Took his leave (apotaxamenos). First aorist middle (direct), old verb, to separate oneself, to bid farewell (Vulgate valefacio), as in Act 18:21; Mar 6:46.
Sailed thence (exeplei). Imperfect active of ekpleō, old and common verb, inchoative imperfect, started to sail. Only Priscilla and Aquila are mentioned as his companions though others may have been in the party.
Having shorn his head (keiramenos tēn kephalēn). First aorist middle (causative) of keirō, old verb to shear (sheep) and the hair as also in 1Co 11:6. The participle is masculine and so cannot refer to Priscilla. Aquila comes next to the participle, but since mention of Priscilla and Aquila is parenthetical and the two other participles (prosmeinas, apotaxamenos) refer to Paul it seems clear that this one does also.
For he had a vow (eichen gar euchēn). Imperfect active showing the continuance of the vow up till this time in Cenchreae, the port of Corinth when it expired. It was not a Nazarite vow which could be absolved only in Jerusalem. It is possible that the hair was only polled or trimmed, cut shorter, not “shaved” (xuraō as in Act 21:24) for there is a distinction as both verbs are contrasted in 1Co 11:6 (keirāsthai ē xurāsthai). It is not clear what sort of a vow Paul had taken nor why he took it. It may have been a thank offering for the outcome at Corinth (Hackett). Paul as a Jew kept up his observance of the ceremonial law, but refused to impose it on the Gentiles.