ויקרא, פרק כ׳, פסוק י״ט

The Torah establishes strict boundaries around family relationships, specifically addressing the intimacy between a nephew and his aunt. The laws surrounding both maternal and paternal aunts reveal a layered approach to family lineage, biological certainty, and the severe consequences of crossing these boundaries. In a section primarily dedicated to outlining the punishments for forbidden relationships, a direct warning is issued instead. The primary approach among commentators is that this repetition serves to expand the scope of the law, clarifying that the restriction applies equally to both maternal and paternal aunts. This is a notable distinction from the laws concerning an uncle's wife, which apply exclusively to the wife of a father's paternal brother.

Both the father's sister and the mother's sister are explicitly mentioned because each carries a unique significance. The father's side of the family dictates the primary lineage, whereas the mother's side provides absolute biological certainty of the blood relation [מזרחי, גור אריה]. By mentioning the mother's sister first, a novel concept is highlighted: she is forbidden to the exact same degree, even though there is no parallel restriction regarding a maternal uncle's wife [מלבי״ם, רד צ הופמן].

The specific language used to describe the forbidden act is carefully selected to prevent any misunderstanding of its scope. If the prohibition had only warned against taking an aunt, one might assume that only formal marriage is prohibited. Conversely, if it only forbade lying with her, one might mistakenly conclude that a formal marriage is permissible, especially since marrying an aunt was an accepted practice before the Torah was given. Therefore, a broader concept is used to encompass both formal marriage and casual encounters [רד צ הופמן]. Alternatively, this phrasing serves as a warning not to marry these relatives even with noble intentions, such as attempting to produce offspring in a manner similar to levirate marriage [שד״ל].

The underlying reason for this strict separation is the close blood tie between the individuals [ביאור שטיינזלץ]. However, the terminology describing the physical act of exposing a close relative also serves as the foundation for a central legal ruling. Since the prohibition against partial physical contact is already established elsewhere for all forbidden human relationships, commentators explain that the phrasing here extends the law to include partial contact with an animal [תורה תמימה, אדרת אליהו]. Furthermore, the anatomical terms usually found in similar laws are deliberately omitted. This omission reflects the physical reality of animals and certain uniquely developed women, where any penetration is immediate and direct without an external vestibule [העמק דבר, הכתב והקבלה].

When such an act is committed willingly by both parties, they equally share the burden of guilt [אבן עזרא, חזקוני]. Unlike other laws that explicitly prescribe the death penalty or childlessness, the consequence here is stated in general terms. The primary approach among commentators is that this refers to the severe spiritual punishment of being cut off from the people [ברכת אשר, רד צ הופמן], though some suggest it means the couple will live out their days without having children [שד״ל]. A unique perspective offers that the phrasing is kept general precisely because it encompasses two distinct consequences: the spiritual punishment of being cut off for relations with an aunt, and the physical death penalty for the aforementioned acts involving an animal [הכתב והקבלה].