Numbers 6:2
Speak unto the children of Israel, and say unto them, When either man or woman shall separate themselves to vow a vow of a Nazarite, to separate themselves unto the LORD: Speak unto the children of Israel, and say unto them, When either man or woman shall separate themselves to vow a vow of a Nazarite, to separate themselves unto the LORD:
Either a man or a woman may separate themselves to the Lord by vowing the vow of a Nazarite. The vow is for a specified term, a period of separation to the Lord. It requires abstaining from wine and strong drink and from everything made of the vine, from the kernels even to the husk, including liquor of grapes and moist or dried grapes. This command is temperance teaching from a Christian standpoint.
John the Baptist was dedicated and consecrated to God as a Nazarite from birth, and he made that consecration his own for life. His consecration meant drinking neither wine nor strong drink and being filled with the Holy Ghost. Samson was to be a Nazarite to God from birth to death, and the same restriction on diet and drink was laid upon his mother for the sake of her unborn child, lest her appetite be transferred to him.
When the vow was nearly complete, days of purification and offerings still remained. The four men, the four believers in Jerusalem, were nearing the end of such a vow, with costly sacrifices still to offer after purification. Paul joined them in the temple ceremonies during the seven days of purification and paid their expenses, to signify that their purification period was being completed and the required offerings would be made.