ויקרא, פרק י״ח, פסוק ז׳

The prohibition of incest between a son and his mother is found in nearly every human culture. It naturally appears at the top of the list of forbidden relationships because a mother is a person's first and most fundamental relative. Within a healthy family structure, the profound shame of such an act affects both parents equally. Because a husband and wife are considered one flesh, violating the mother's dignity is a direct assault on the father's honor and brings disgrace upon the entire family [ביאור שטיינזלץ, אבן עזרא, פירושן של נשים, ביאור יש״ר].

A fundamental discussion among commentators surrounds the exact nature of the offense against the father. The primary approach, following the plain meaning of the text, maintains that there is only a single prohibition being presented: a son engaging in relations with his mother. In this view, the offense against the father and the offense against the mother refer to the exact same woman. By committing this act, a son is guilty of a double evil. He violates his mother's privacy while simultaneously violating his father's, since the intimacy of the mother inherently belongs to the father [רמב״ן, הטור הארוך, רבנו בחיי, שד״ל, רד״צ הופמן].

Conversely, many commentators rely on rabbinic traditions to split the instruction into two distinct prohibitions, though they differ on how to define them. One perspective explains that the offense against the father actually refers to relations with the father's wife, even after the father has died. The subsequent mention of the mother is then understood as a separate rule forbidding a biological mother who was never married to the father, such as in cases where the son was born from rape or seduction [רש״י, מזרחי, גור אריה, בכור שור, מלבי״ם]. Another group follows the Talmudic sages who interpret the offense against the father entirely literally. They view it as a strict ban on a son engaging in homosexual relations with his own father. A person who commits this act would violate two separate laws: the general prohibition against homosexual relations and the specific restriction regarding a father [תורה תמימה, רלב״ג, הכתב והקבלה, ברטנורא].

It is also noted that the masculine phrasing of the instruction implies it is not addressing a daughter's actions toward her father. In such a tragic scenario, it is the father who initiates and commits the violation against her, rather than the reverse [ברכת אשר על התורה]. Nonetheless, the broader laws of forbidden relationships apply equally to both men and women [רד״צ הופמן]. Ultimately, the biological reality of motherhood stands as the absolute foundation for this restriction. Regardless of her legal or marital status with the father, a mother is forbidden to her son simply because she gave him life. Any violation of this boundary is considered a severe corruption of the very root of human existence [רמב״ן, רש״י, מלבי״ם].