Adapted from discourses of the Alter Rebbe and the Tzemach Tzedek by Rabbi Yossi Marcus
The soul of man is made up of two general parts: one that remains beyond and above the body and one that is enclothed within it. The first aspect does not undergo the process of Divine concealment administered to the second aspect. Thus it remains aloof from the body and is not affected by its distorted view of reality. This part of the soul is called mazal, as in the saying, “although he does not see it, his mazal sees it.”
The Talmud identifies those who were with Daniel as Chaggai, Zechariah and Malachi, who, although prophets themselves, were not on the level of Daniel and therefore could not see what he saw. The Talmud then asks: If they did not see, why were they frightened? And the Talmud answers: Though they did not see, their mazals did see. Ravina commented: Learn from this that one who becomes frightened (for no apparent reason, it is because) though he did not see it (the cause for his fear), his mazal did see it.
In other words, although a person is not consciously aware of his mazal, he is affected by what the mazal experiences. Thus if the mazal is afraid, the person will be afraid. If the mazal is inspired, the person will suddenly and inexplicably feel inspired. The mazal, therefore, because of its superior vision, guides the person through certain decisions, causing him to choose the path that will best serve his ultimate purpose.]
It is called mazal, a word that can connote “flowing,” since the energy of the mazal flows to the aspect of the soul that inhabits the body.
The mazal aspect of the soul is referred to as yisfas toar, “beautiful appearance.” Beauty is produced by the coming together of various elements. One color does not create beauty. It is the convergence of various colors that creates beauty. Similarly, the mazal receives its energy from a number of Divine elements and is therefore related to the sefirah of Tiferes, which is the fusion of Chessed (kindness) and Gevurah (severity), as is known to those who know the hidden wisdoms.
[The soul is therefore often referred to as Yaakov, who represents the fusion of Avraham and Yitzchak, kindness and severity.]
The aspect of the soul that inhabits the body is called “a woman of beautiful appearance,” meaning that it is the recipient of the beauty of the higher aspect of the soul.
[In Kabbalah, woman symbolizes reception, while man symbolizes giving. (This is reflected in the process of procreation, wherein the woman receives from the man.)]
Hence she is referred to as a woman in captivity, since the lower aspect of the soul is, so to speak, held captive by the mental and emotional chains of the bodily perspective.
So when a person “desires her”—he truly wishes to free the imprisoned soul from its captivity, he must “shave her head” and “cut her nails.”
The Torah’s attitude towards hair is seemingly conflicted. The Nazir’s hair is holy; the Levite in the desert had to shave his hair. The beard and payos should not be touched; a woman’s hair must be covered. The hair of the leper and the “yefas toar” must be shaved; the hair of Shimshon was the source of his strength.
In the supernal worlds as well we find this paradox. The “hair” of atika kadisha is the source of life for all worlds.
[Atik, “ancient,” or “detached” refers to the sphere that is beyond the order of creation. In Atik, the Zohar says, “there is no left side”—it is beyond the source for concealment. The “hairs of Atik,” though, i.e., the energy of Atik extremely filtered, serves as the source of creation. For creation can only come into being through the concealment of the Divine.]
The hair of nukva (Malchut), by contrast, is a source of vitality for negative energies.
Hair represents extreme filtering of vitality, tzimtzum. (A person therefore experiences no pain when his hair is cut.) The energy found in the hair is the “surplus of the brain.” Therefore, the source of the hair or “surplus,” will determine whether the hair is positive or negative.
Example: The Zohar cites the custom of Rabbi Hamnuna the Elder, who would preface his teachings of wisdom with a teaching of “shtus,” foolishness. (Similarly the Talmud tells of Rabba’s custom to preface his lectures with a joke.) Obviously, this does not mean literal foolishness, G-d forbid. Rather, this refers to the “surplus” of his wisdom, which is compared to hair.
The “surplus” of the brain of a mystic, what is called “foolishness” and a “joke,” contains deep wisdom. As the Talmud comments—on the verse in Pslams regarding the righteous, its leaf does not wither—“The mundane talk of scholars should be studied.” Even the leaf of the righteous, which is subordinate to the main thing, the fruit, is substantial and does not wither. Similarly his “mundane” talk, which is subordinate to his principal wisdom, is substantial and requires analysis.
Such surplus, or hair, can be compared to the hair of Atik, which is only goodness.
On the other hand, the “brain surplus” of the average person, his shtus, or joke or mundane talk does not contain any wisdom and in fact distracts him from Divine consciousness.
Similarly, the “hair” of nukva, the extreme filtering of Malchut, which is the lowest sefirah and is within the order of creation, allows for the sustenance of negative forces.
Thus the hair of the Nazir (or the beard and payos of any man), which derives its energy from Atika kadisha, as the Arizal writes in Parshas Naso, should not be cut.
The hair of a woman, by contrast, which derives from nukva of Atzilut, must be covered, since it can allow for the sustenance of negative forces.
[The Tzemach Tzedek also compares hair to a parable. The parable is an indirect expression of the principal wisdom and allows a person of lower understanding to perceive the wisdom of a great sage, which would otherwise be inaccessible. A metaphor given by a fool, or even one whose wisdom is not profound, is empty words, since the idea can be conveyed directly.]
On a personal level, the hair of the captive soul, which must be shorn refers to the scattering of the soul’s energies—its mind and heart—to worthless endeavors. This is the “surplus” of the soul, which must be cut off in order for the soul to reconnect with its higher aspect, its mazal.
A person must also cut off “the nails,” i.e., the surplus of the hand, which is called Chessed. [The hand is used to do kindness.] (As in the case of Avraham, who embodies Chessed, the surplus of his energies resulted in Yishmael.) When this is accomplished, the soul’s energies are redirected entirely through the fulfillment of Torah and mitzvos and it is freed from its captivity. &
 Likutei Torah p. 36a ff. and Derech Mitzvosecha p. 208 ff.
 The Talmud (Yevamos 48a) cites a disagreement between Rabbi Eliezer and Rabbi Akiva as to the meaning of “make her nails.” According to Rabbi Akiva, the opinion cited by Rashi, this means “let her nails grow” so that they become disgusting. According to Rabbi Eliezer, the opinion cited by Chizkuni, this means “cut her nails.” The maamar apparently follows the latter opinion.
 Deuteronomy 21:10-14.
 On the literal level, this law addresses the inevitable occurrence during war of a soldier desiring to marry one of the captive women. The Torah reluctantly allows him to do so. But, she must first undergo a process that is hoped to discourage him from marrying her. If he decides not to marry her, he is not allowed to sell her or use her in anyway. If he does marry her, she is to be accorded full rights as any other married woman.
 Megilah 3a.
 Thus the Baal Shem Tov explained the purpose of the bas-kol, or “heavenly voice” that makes various declarations. But if nobody hears them, what use are they? The answer: you may not hear it, but your mazal does. See the Rebbe’s commentary on Pirkei Avot 6:2.
 See, for example, Likutei Sichot 30:223 fn. 24, cited in Yosef Jacobson’s essay “Souls on the Fringe,” fn. 16.
 Shabbos 30b.
 Psalms 1:3.
 Sukkah 21b.