Hebrew: form Nazirite
the name of such Israelites as took on them the vow prescribed in Numbers 6:2-21
The word denotes generally one who is separated from others and consecrated to God. Although there is no mention of any Nazarite before Samson, yet it is evident that they existed before the time of Moses.
The vow of a Nazarite involved these three things,
abstinence from wine and strong drink,
refraining from cutting the hair off the head during the whole period of the continuance of the vow, and…
the avoidance of contact with the dead.
When the period of the continuance of the vow came to an end, the Nazarite had to present himself at the door of the sanctuary with…
a he lamb of the first year for a burnt-offering
a ewe lamb of the first year for a sin-offering
a ram for a peace-offering
After these sacrifices were offered by the priest, the Nazarite cut off his hair at the door and threw it into the fire under the peace-offering.
For some reason, probably in the midst of his work at Corinth, Paul took on himself the Nazarite vow. This could only be terminated by his going up to Jerusalem to offer up the hair which till then was to be left uncut. But it seems to have been allowable for persons at a distance to cut the hair, which was to be brought up to Jerusalem, where the ceremony was completed. This Paul did at Cenchrea just before setting out on his voyage into Syria (Acts 18:18).
On another occasion (Acts 21:23-26), at the feast of Pentecost, Paul took on himself again the Nazarite vow.
“The ceremonies involved took a longer time than Paul had at his disposal, but the law permitted a man to share the vow if he could find companions who had gone through the prescribed ceremonies, and who permitted him to join their company. This permission was commonly granted if the new comer paid all the fees required from the whole company (fee to the Levite for cutting the hair and fees for sacrifices), and finished the vow along with the others.
Four Jewish Christians were performing the vow, and would admit Paul to their company, provided he paid their expenses. Paul consented, paid the charges, and when the last seven days of the vow began he went with them to live in the temple, giving the usual notice to the priests that he had joined in regular fashion, was a sharer with the four men, and that his vow would end with theirs.
Nazarites retired to the temple during the last period of seven days, because they could be secure there against any accidental defilement” (Lindsay's Acts).
As to the duration of a Nazarite's vow, every one was left at liberty to fix his own time. There is mention made in Scripture of only three who were Nazarites for life: Samson, Samuel, and John the Baptist (Judges 13:4,5; 1 Samuel 1:11; Luke 1:15).
This institution was a symbol of a life devoted to God and separated from all sin, a holy life.