Likutei Moharan 21:6/ליקוטי מוהר"ן כ״א:ו׳

16. This is the reason for the spittle of the levirate ceremony. It is written (Deuteronomy 25:9), “She shall spit toward his face”—specifically his face. For this one [her first husband] remains without offspring. He did not leave a blessing after him that they might draw the intellect of the face into the world through their good deeds. And his brother does not want to perpetuate the name of his deceased brother and does not want to marry her.

2Because of this, “She shall spit toward his face.” For he does not want to draw the dead man’s soul into the world so that he might rectify the light of the face. And occasionally, in this spittle appears the face of the departed. The departed’s face —specifically. With this spittle he [the brother] is shamed, and embarrassment is mainly [exhibited] in the face. And this is because he did not want to establish the name of his deceased brother.

3{“This is not true of my servant Moshe. He is the mo st tru st ed of all My house. Face to face I speak with him… a true picture of God he beholds… Miriam became leprous… Let [Miriam] not be as one dead, who comes from the womb of his mother with half his flesh eaten away… Moshe prayed, El, please heal her… If her father had spit in her face, would she not be embarrassed for seven days? … For seven days, Miriam remained quarantined outside the camp…” (Numbers 12:7-15).} And this is the concept of (Numbers 12:14), “If her father had spit in her face, would she not be embarrassed for seven days?” Specifically “seven days”—the seven clouds by which the face of the menorah shines. But he refused to establish the name of his deceased brother, and therefore “she shall spit toward his face”—i.e. shamefaced.

4This is what our Sages said (Yevamot 52a): “The levirate sister-in-law is taken [as a wife] through a proclamation.” This is the opposite of embarrassment, corresponding to (Psalms 29:9), “All proclaim, ‘Glory!’”‘—the opposite of “embarrassed for seven days.”

5And Miriam, in blemishing the glory of Moshe—he being synonymous with the Godly influx, as in (Exodus 34:30), “For the skin of his face shone brilliantly”—blemished the concept of the seven candles. This is because Moshe was humble, self-effacing and patient. His being shamed did not make him angry, which is the perfection of the aspect of nose. And it is written of him (Numbers 12:8), “Face to face I speak with him”—this is <the perfect sanctification of> the aspect of mouth. And it is written of him (ibid.), “A true picture of God he beholds”—this is <the perfection of> the aspect of eyes. And it is written of him (ibid.:7), “He is the most trusted of all My house”—this is <the perfection of> the aspect of ears, corresponding to (Proverbs 11:13), “A trustworthy spirit conceals the matter,” as brought in the Zohar .

6Because of this, she became leprous. “Leprosy is the SeGiRu (the containment) of the supernal light” (Zohar III, 49b) —i.e. the light of the face, mentioned above. And it is written of her (Numbers 12:15), “For seven days, she remained SaGaR (quarantined) outside the camp.”

7And this is what Aharon requested (ibid. 12:12): “Let [Miriam] not be as one dead, who comes from the womb of his mother with half his flesh eaten away.” Because of the containment of the supernal light, she is in the category of the dead, for “a leper is considered as dead” (Nedarim 64b).

8“Who comes from the womb of his mother.” This is the concept of the levirate marriage. By means of the levirate marriage, his wife is his mother—his wife becomes his mother.

9“With half his flesh eaten away.” In other words, he has no mate. This is because “husband and wife are two halves of a body” (Zohar III, 109b). But now that his wife is his mother, the result is that half his flesh has been eaten away and there is no marriage partner for him.

10{The explanation is as follows: When someone dies without children, his wife must undergo levirate marriage. As a result of this marriage, the dead man is reincarnated as the son born to his wife after she married his brother. As is explained in the Saba (Zohar II, 100b), “His wife is his mother.” That is, it is great suffering and punishment for the deceased that his wife becomes his mother. For now he has to be born to his wife, who becomes his mother. Because of this, without great mercy [from Heaven], it is impossible for the son born to this woman, who has undergone levirate marriage, to find his marriage partner (as is brought in the Zohar I, 92a, that it is said of him: “Perhaps another will precede him—with mercy.” See there.)

11For this son of the woman who has undergone levirate marriage—who is in truth her husband, with his wife becoming his mother—has no marriage partner now that his mate has become his mother. This is what Rabbi Nachman explains: Aharon pleaded for Miriam who had blemished the intellect of the face, which is the blemish of the one who dies without offspring, that she should not, God forbid, be made to suffer the punishment of a levirate marriage. This is: “Let [Miriam] not be as one dead, who comes from the womb of his mother.” She should not be like one who dies without children, who must again emerge in reincarnation from his mother’s womb—i.e., his wife becomes his mother. That because of this: “half his flesh [is] eaten away”—namely, half his body is consumed. In other words, he has no marriage partner, for she is half his flesh, half his body, as explained.}