The Torah in Parashat Naso (Bamidbar 6:5) commands that one who takes a vow to be a Nazir must allow his hair to grow throughout the period of Nezirut to which he committed (“Gadel Pera Se’ar Rosho”).
In discussing this command, the Sefer Ha’hinuch elaborates on the concept of Nezirut and the purpose of this observance. He explains that the human being is comprised of two components – the spirit, which is the primary element of our beings, and the body, which the Sefer Ha’hinuch compares to a “house.” The body’s purpose is subordinate to that of the spirit, and serves only to facilitate our involvement in spirituality. Our challenge, the Sefer Ha’hinuch writes, is to focus the bulk of our attention on the spirit, but without neglecting our body, the “house” of the spirit. As G-d wanted us to fulfill our spiritual purpose through the medium of our physical components, we are to maintain the body and tend to our physical needs in order that it will function property and serve as the vehicle that it is meant to serve for spiritual pursuits. The Nazir is thus considered special, the Sefer Ha’hinuch explains, because he seeks to limit his physical engagement without neglecting his physical needs entirely. He abstains from wine, which is not a necessity for his physical wellbeing, and he refrains from haircutting, which shows a disregard for his appearance, thereby signifying a diminished focus on the body and the physical elements of his being. This has the effect of subduing the Yeser Ha’ra (evil inclination), and thus puts the Nazir in a better position to fulfill the purpose for which G-d created him. The Torah requires a Nazir to remove all his hair at the conclusion of his period of Nezirut, because this, too, displays a disregard for his appearance, and thus shows a preoccupation with the spirit instead of a preoccupation with the body.
The Sefer Ha’hinuch references in this context the story told in Masechet Nedarim (9) of Shimon Ha’sadik, who met a young, nice-looking man with beautiful hair, who took upon himself the nazirite vow. Shimon Ha’sadik asked the young man why he undertook such a measure, and the man explained that he made this decision in order to ensure that he would not fall prey to his Yeser Ha’ra. This response made an impression on Shimon Ha’sadik, who praised the young man and expressed his wish that there should be many more people like him.
The question arises, however, as to why, after the completion of the Nazir’s period of refraining from wine and haircutting, he is required to offer a sin-offering for atonement. If he is considered special and sacred for undertaking measures to heighten his focus on spirituality, and to subdue his evil inclination, then why does he require a sin-offering? The Gemara cites an opinion that the Nazir brings an atonement offering because “Si’er Asmo Min Ha’yayin” – he deprived himself of wine. This seems, at first glance, to contradict the Sefer Ha’hinuch’s analysis of the concept of Nezirut, viewing it as an admirable process of diminishing one’s preoccupation with physical enjoyment.
The Sefer Ha’hinuch answers this question by explaining that all people are different and have different needs; that which is a noble measure of moderating physical engagement for one person is irresponsibly extreme for another person. it is thus possible that the Nazir may have extended too far in seeking to intensify his focus on spirituality, to the point where his term of Nezirut is deemed inappropriate. Therefore, in case the Nazir’s period of self-denial was excessive, he must bring a sin-offering to atone for depriving himself unreasonably.
The Ramban advances an entirely different explanation for why the Nazir is required to bring a sin-offering after observing his period of Nezirut. He writes that to the contrary, the Nazir requires atonement for ending his observance of a higher standard of spiritual focus. After living on an especially high standard of Kedusha, he now resumes drinking wine and cutting his hair, instead of continuing his observance of Nezirut forever. For this reason, the Ramban writes, the Nazir must bring a sin-offering to earn atonement.
If a Nazir cut his hair with a razor, even if he did so accidentally, or under duress, the term of Nezirut that he had observed is rendered invalid, and he must begin his term anew. However, this applies only if he cut the majority of his hair; if he cut less than the majority of his hair, then his observance is not disqualified.
Exposure to Tum’at Met (the impurity resulting from contact with a human corpse) likewise invalidates the Nezirut and requires beginning the period anew, even if this happened accidentally, such as if the Nazir was with somebody who suddenly died. However, drinking wine does not invalidate the Nezirut.
If a person declared himself a Nazir using a “Kinui” – a “slang” term that refers to Nezirut, his vow is binding. For example, if instead of declaring, “Hareni Nazir” (“I am hereby a Nazir”), one says, “Hareni Nazik,” “Hareni Naziach” or “Hareni Baziach,” he becomes a Nazir, because these terms refer to a Nazir. The same is true of “Yadayim” – meaning, incomplete declarations. For example, if a Nazir passes by a person, and he says, “Eheh” (“I shall be”), then he becomes a Nazir, even though he did not complete the sentence by saying, “Eheh Nazir.”
A father is empowered to declare Nezirut upon his child if his child is a minor, before the age of Bar-Misva. Furthermore, a father is empowered to override his young daughter’s declaration of Nezirut, and also his wife’s declaration of Nezirut.
This command applies to both men and women, as both can become a Nazir. It applies in all places and in all times, even nowadays, in the absence of the Bet Ha’mikdash, and thus one who declares himself a Nazir nowadays may not cut his hair. However, since the term of Nezirut ends with the offering of special sacrifices, and we cannot offer sacrifices nowadays, one who declares Nezirut nowadays becomes a Nazir forever. He is forced to move to Israel and live there until either he dies or the Bet Ha’mikdash is rebuilt and he can offer the required sacrifices.