'Vow' in the Bible

And Paul after this tarried there yet a good while, and then took his leave of the brethren, and sailed thence into Syria, and with him Priscilla and Aquila; having shorn his head in Cenchrea: for he had a vow.

Do therefore this that we say to thee: We have four men which have a vow on them;

Then Paul took the [four] men, and the next day he purified himself along with them [by submitting to the ritual]. He went into the temple to give notice of [the time] when the days of purification [ending each vow] would be fulfilled and the usual offering could be presented on behalf of each one.