Beginning with this verse the church elders explain to Paul what they think is best for him to do in light of the situation. It is generally assumed that the vow referred to was a Nazirite vow (see 18.18). In ancient Israel it was customary for some men to take a lifelong vow to abstain from wine or anything unclean, and never to cut their hair (note Samson in Judges 13). Later the Jewish Law provided for a man to assume a temporary Nazirite vow, which meant that he would live as a Nazirite for a certain length of time, and at the end of that time offer a series of sacrifices. When all of this had been completed, the man shaved his head and burned the hair along with the sacrifice. After this he was free to drink wine and to go back to his normal way of life. It is known from rabbinic sources that the shortest length of time for which one could assume this temporary vow was 30 days, so this raises problems with the mention of seven days in verse 27. A number of solutions have been offered, but it must be admitted that none of these are without their particular difficulties. Perhaps the least complicated conclusion is to assume that these men who had taken the vow had in the meanwhile become defiled. Therefore, it was necessary for them to undergo a period of seven days purification, at the end of which they would be permitted to offer the sacrifices required by the Jewish Law (see Numbers 6.9-12).

The term vow may be rendered as “a promise made before God” or “a strong promise made to God.” The process of “taking a vow” in some languages may actually be rendered as “bound themselves by a promise to God.”

Quoted with permission from Newman, Barclay M. and Nida, Eugene A. A Handbook on The Acts of the Apostles. (UBS Handbook Series). New York: UBS, 1972. For this and other handbooks for translators see here .