Our Gemara on Amud Aleph states that according to the opinion of אין שאלה בהקדש, one cannot annul vows made for sanctification purposes, one also cannot annul a nazirite vow. Tosafos offers a proof text that Nazirhood is a sacrament (Bamidbar 6:5):

קָדֹ֣שׁ יִהְיֶ֔ה גַּדֵּ֥ל פֶּ֖רַע שְׂעַ֥ר רֹאשֽׁוֹ׃

He shall be holy, the one who grows the hair of his head.

The simple understanding is that the essence of the Nazir’s holy attainment is his abstention and separation from the frivolity of this world. Denying his physical appearance and care by letting his hair grow unkempt represents the goal of his Nazirhood. So important is this hair, that it physically is included in the votive material of the sacrifice and burned along with the Shelamim (Bamidbar 6:18).

There is more depth to this idea. The Zohar (Nasso 127b) likens the hair of the Nazir to a symbolic representation of “Ancient of Days” (a manifestation of God in Daniel’s vision), as described in Daniel (7:9):

חָזֵ֣ה הֲוֵ֗ית עַ֣ד דִּ֤י כׇרְסָוָן֙ רְמִ֔יו וְעַתִּ֥יק יוֹמִ֖ין יְתִ֑ב לְבוּשֵׁ֣הּ ׀ כִּתְלַ֣ג חִוָּ֗ר וּשְׂעַ֤ר רֵאשֵׁהּ֙ כַּעֲמַ֣ר נְקֵ֔א כׇּרְסְיֵהּ֙ שְׁבִיבִ֣ין דִּי־נ֔וּר גַּלְגִּלּ֖וֹהִי נ֥וּר דָּלִֽק׃

As I looked on, Thrones were set in place, And the Ancient of Days took His seat. His garment was like white snow, And the hair of His head was like lamb’s wool. His throne was tongues of flame; Its wheels were blazing fire.

Likkutei Torah (Emor 1) explains that just as the hair is nominally attached to the head (intellect), but also essentially dead material and not strongly connected, so too in regard to manifestations from God in this world. God’s spiritual emanations find their way into this world, but like the hair on the head, it is mostly devoid of the full power and life from where it originated from. The Nazir, in his efforts to transcend this world, gives more life and becomes more connected to God’s emanations, as symbolized in the hair.

I am going to add a thought. A person’s hair contains a record of what occurs in the body, much as tree rings record the years in a tree trunk. Believe it or not, evidence of trauma is recorded in the hair with increased indicators of cortisol, the stress hormone. (See references at the end of this essay.). As we saw in Psychology of the Daf Nazir 2, the Nazir witnessed a disturbing event, and as a result saw fit to enter into a focused reclusive state of self-abnegation.  His trauma was stored in his head and even his hair.  Upon completion of his Nazirhood, he is ready to move on and shed his past by shedding his hair,

References:

“Hair cortisol concentrations in war-affected adolescents: A prospective intervention trial”, Psychoneuroendocrinology, Volume 89, March 2018, Pages 138-146. https://www.sciencedirect.com/science/article/pii/S0306453017312076 

Hair cortisol predicts avoidance behavior and depressiveness after first-time and single-event trauma exposure in motor vehicle crash victims. 

Katja Petrowski, Susann Wichmann, Jaroslav Pyrc, Susann Steudte-Schmiedgen & Clemens Kirschbaum

Pages 567-576 | Received 05 Sep 2018, Accepted 02 Jan 2020, Accepted author version posted online: 15 Jan 2020, Published online: 14 May 2020

https://www.tandfonline.com/doi/full/10.1080/10253890.2020.1714585

Translations Courtesy of Sefaria, except when, sometimes, I disagree with the translation

Do you like what you see? Please subscribe and also forward any articles you enjoy to your friends, (enemies too, why not?)