Purify thyself with them... — This involved sharing their abstinence for the uncompleted term of the vow, and shaving the head at its conclusion.
Be at charges with them... — Literally, spend money on them. This involved payment (1) for the act of shaving the head, for which probably there was a fixed fee to priest or Levite; (2) for the sacrifices which each Nazarite had to offer — sc., two doves or pigeons, a lamb, an ewe lamb, a ram, a basket of uneavened bread, a meat offering and a drink offering (Numbers 6:9-12).