The Prohibition of Forbidden Sexual Relations

Do not commit adultery
Defining the Boundaries of Intimacy

The Meaning

One of the most powerful human desires is the desire for sexual fulfillment, which is necessary for procreation and thus the continuation of humanity. But when used destructively, it has not only destroyed the morals of individuals, but it has also been proven to lead to the disintegration of whole societies.

The Hebrew words for man (ish) and woman (ishah) both contain the Hebrew root word aish, fire. The Talmudic Sages drew a correlation between the words: just as fire can be harnessed to produce energy and provide great benefit, but when unleashed it can also bring destruction and ruin, so too, human sexual desire must be kept within the boundaries of a productive and G-dly marriage.

From the Introduction by Arthur Goldberg, author of “Light in the Closet,” to the section on the Prohibition of Forbidden Relations, in “The Divine Code,” Part VI:

The Torah places much emphasis on the value of the family and the furtherance of societies.  Wholesome families are the foundation upon which healthy communities, nations, and societies are built.  Without a foundation, the mightiest building is bound to crumble.   As explained in the Written Torah and Talmud,  a main accomplishment of the sexual prohibitions is rejection of unbridled licentiousness that leads to the disintegration of society.  The modern vision of morality (which mirrors much of ancient paganism) is often rationalized as a virtually all-permissive, “anything goes” social system founded on a concept of universal “tolerance”. Unfortunately, this concept of tolerance is, in actuality, a facade used to mask an agenda of sexual licentiousness.

History confirms the importance of these Torah lessons. The British anthropologist J. D. Unwin’s comprehensive and classic study of 5,000 years of history chronicles the historical decline of 86 primitive and civilized societies. He found that “the regulations of the relationship between the sexes” are the very foundation of civilized society.[1] Unwin discovered (contrary to his personal philosophy and inclination as a social liberal) a distinct correlation between increasing sexual freedom and social decline.

If the authentic Torah teachings on true sexual morality are followed, humankind will hopefully not self-destruct. G-d provided a rainbow as evidence of His covenant that He will not destroy the world again. The seven colors of the rainbow correspond to the Seven Noahide Laws – the foundations of a G-dly and ordered society. But because G-d endowed mankind with free choice, there is the ever-present question concerning whether a society will heed them – particularly the admonitions of sexual boundaries and proscriptions. These are set forth as a code of laws involving sexuality. If Gentiles live their lives in ways that are consistent with this Biblical framework of morality, then the rainbow can also represent a multi-level system of spiritual wholeness that enables them to live righteous lives and have a share in the World to Come. This then becomes the opportunity for a covenant between humans, and a basis upon which we can create a world of wholeness and holiness.


[1] J. D. Unwin, Sex and Culture, Oxford Press, 1934.

Scriptural Sources

Five of the six types of relations that are forbidden by G-d to Gentiles are covered in Genesis 2:24: “Therefore a man shall leave his father and his mother and cling to his wife and they shall become one flesh.” This verse explicitly forbids relations with one’s mother, one’s father’s wife, a wife of another man, another male, and an animal. A Gentile is also forbidden to have relations with his maternal sister, which is learned from Genesis 20:13: “Moreover, she is indeed my sister, my father’s daughter, though not my mother’s daughter; and she became my wife.” (Note that Abraham said this to appease Abimelech. It was actually only figuratively true in his case, since Sarah was the daughter of Abraham’s brother. They had the same paternal grandfather, whom people often referred to as “father”.) It was also universally accepted that father-daughter relations would be prohibited, as evidenced by the disgrace of Lot after he had relations with his two daughters, following G-d’s destruction of Sodom and Gomorrah (Genesis 19:29-36, and Rashi’s explanation of Genesis 20:1). Relations between females are likewise an abomination to G-d. This is one of the subjects of the verse Leviticus 18:3, which speaks against the immoral practices of the ancient Egyptians and Canaanites, and which Leviticus 18:30 refers to as “abominable traditions.” About these the Midrash specifies: “A man would marry a man, a woman would marry a woman, and a woman would be married to two men.”

Some Details and Related Principles

Adapted from the Table of Contents of The Prohibition of Forbidden Relations, in “The Divine Code,” Part VI:

  • Categories of forbidden sexual partners and sexual acts.
  • The prohibitions of homosexual and bestial relations.
  • The prohibition of relations with other men’s wives.
  • Partners with whom there can be no status of marriage.
  • Precepts related to marriage, fornication, and divorce.
  • Precepts related to spilling semen and contraception.
  • Guarding against forbidden relations, and following ways of modesty.
  • Prohibitions related to being alone with a forbidden partner.

Selected rules related to the Noahide prohibition of forbidden relations, from “The Divine Code”, Part VI:

  • A few other sexual relations that are not capital sins for Gentiles are also forbidden. For example,  a full sister or maternal half-sister of a man’s mother is forbidden to him.
  • If Gentile societies see a need to impose upon themselves extra restrictions, and enforcedly prohibit relations between other categories of relatives, they are permitted to do so. (For example, almost all societies have prohibited marriage between an uncle and his niece.)
  • There is no status of true marriage for those who are minors according to Torah Law, since they do not have the maturity of mind to accept a marital bond. An even higher minimum age at which to allow and recognize marriages should be set by some communities. This should be the age when most people in that community are considered to be mature and responsible for their actions. Nowadays, this is usually in the late teens.
  • G-d’s words (Genesis 2:24), “Therefore a man shall leave his father and his mother and cling to his wife, and they shall become one flesh,” reveal that it is natural and appropriate for a man to marry a woman and establish a family. One who deviates from this path acts contrary to what G-d intended for mankind.

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More Information

AskNoah Forum on the Prohibition of Forbidden Relations

“Rights” or Ills?

NEW External link: Letter from the Lubavitcher Rebbe to Man Struggling with Homosexuality (1986)

Books and CD’s:

Light in the Closet

Doesn’t Anyone Blush Anymore? Reclaiming Intimacy, Modesty and Sexuality

A New Twist to an Old Story

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