The Torah in Parashat Ahareh-Mot (Vayikra 18:7) forbids “revealing the nakedness” of one’s mother – meaning, engaging in intercourse with her. The Rambam writes that the Torah forbade intercourse with family members because it seeks to promote moderation in the area of intimate relationships, and to prevent a person from excessive involvement in such activity. Since a person’s family members are generally nearby and accessible, the Torah forbade intimacy with family members, with whom he would otherwise be able to frequently cohabit. Additionally, the Rambam writes, intercourse with a family member is inherently shameful, and thus forbidden by the Torah. The Ramban disagrees with the Rambam’s analysis, noting that if this were the Torah’s intent in forbidding incestuous relationships, then it wouldn’t have allowed a man to marry multiple wives. According to Torah law, a man is allowed to marry as many women as he wishes. The Ramban therefore argues that there must be reasons “Al Pi Ha’sod” (based on Kabbalistic concepts) why intimate relationships with family members are not allowed. If one has relations with his mother who is also his father’s wife, then he has transgressed two prohibitions – the prohibition against intercourse with one’s mother, and the prohibition against intercourse with one’s father’s wife. This applies even if after the father’s death; intercourse with his wife, who is also one’s mother, transgresses both these prohibitions, since she had been married to the father. The Sages extended this prohibition to include relations with one’s mother’s mother – that is, his maternal grandmother. This enactment applies also to the maternal grandmother’s mother, and her mother, and so on. Likewise, the Sages enacted a prohibition forbidding intercourse with one father’s mother – his paternal grandmother – and her mother, and so on. Intercourse is forbidden also with one’s grandfather’s mother. This prohibition, of course, applies in all places and in all times. One who committed such an act intentionally is liable to Karet (eternal excision from the Jewish Nation), and if witnesses saw the violation, then he is liable to Sekila (execution through stoning). If one transgressed this prohibition unintentionally, then he is required to offer a Hatat (sin-offering). In the case of a relationship forbidden by force of Rabbinic enactment, one is liable to lashes Mi’de’rabbanan (by force of the Rabbis’ decree).