Terms of Taboo: What Is the Moral Basis for the Sexual Prohibitions?
Leviticus dedicates nearly two entire chapters, 18 and 20, to prohibitions against incest and other violations of sexual mores.  Though most people view incest (e.g., mother-son, father-daughter, brother-sister) as categorically wrong, they are hard-pressed to explain why, yet some form of incest prohibition holds sway in most human societies.
Indeed, the psychological power of this taboo is underlined by its persistence even in modern Western culture, which tends to stress mutual consent as the primary criteria for moral acceptability. The extended lists of prohibited sexual relations in Leviticus 18 and 20 may not be everyone’s first choice of reading material, but they provide insight into the moral basis of these taboos.
The sexual prohibitions of Leviticus 18 use the language of לגלות ערוה “revealing nakedness,” combined with various forms of motive clauses. The list in Leviticus 20 prohibits essentially the same acts, but differs in its language, in the order of its presentation, and the inclusion of penalty clauses.
In both chapters, a handful of the prohibitions include terms of condemnation as an explanation of sorts, ostensibly to highlight something especially egregious about a given act. Do these terms give us any insight into what bothers the author specifically? Let’s look at each one.
The term toevah (תּוֹעֵבָה) is the most widely attested term of condemnation in the Bible. Here it is used in both chapters to condemn male homosexual congress:
ויקרא יח:כב וְאֶת זָכָר לֹא תִשְׁכַּב מִשְׁכְּבֵי אִשָּׁה תּוֹעֵבָה הִוא.
Lev 18:22 Do not lie with a male as one lies with a woman; it is a toevah.
ויקרא כ:יג וְאִישׁ אֲשֶׁר יִשְׁכַּב אֶת זָכָר מִשְׁכְּבֵי אִשָּׁה תּוֹעֵבָה עָשׂוּ שְׁנֵיהֶם מוֹת יוּמָתוּ דְּמֵיהֶם בָּם.
Lev 20:13 If a man lies with a male as one lies with a woman, the two of them have done a toevah; they shall be put to death—their bloodguilt is upon them.
While it is not used to describe any of the other specific acts in either chapter, it is the used multiple times in chapter 18’s conclusion, which spells out the ramifications for violating these norms:
ויקרא יח:כו ...וְלֹא תַעֲשׂוּ מִכֹּל הַתּוֹעֵבֹת הָאֵלֶּה הָאֶזְרָח וְהַגֵּר הַגָּר בְּתוֹכְכֶם. יח:כז כִּי אֶת כָּל הַתּוֹעֵבֹת הָאֵל עָשׂוּ אַנְשֵׁי הָאָרֶץ אֲשֶׁר לִפְנֵיכֶם וַתִּטְמָא הָאָרֶץ. יח:כח וְלֹא תָקִיא הָאָרֶץ אֶתְכֶם בְּטַמַּאֲכֶם אֹתָהּ כַּאֲשֶׁר קָאָה אֶת הַגּוֹי אֲשֶׁר לִפְנֵיכֶם. יח:כט כִּי כָּל אֲשֶׁר יַעֲשֶׂה מִכֹּל הַתּוֹעֵבוֹת הָאֵלֶּה וְנִכְרְתוּ הַנְּפָשׁוֹת הָעֹשֹׂת מִקֶּרֶב עַמָּם. יח:ל וּשְׁמַרְתֶּם אֶת מִשְׁמַרְתִּי לְבִלְתִּי עֲשׂוֹת מֵחֻקּוֹת הַתּוֹעֵבֹת אֲשֶׁר נַעֲשׂוּ לִפְנֵיכֶם וְלֹא תִטַּמְּאוּ בָּהֶם אֲנִי יְ־הוָה אֱלֹהֵיכֶם.
Lev 18:26 …you must not do any of those toevot, neither the citizen nor the stranger who resides among you; 18:27 for all those toevot were done by the people who were in the land before you, and the land became defiled. 18:28 So let not the land spew you out for defiling it, as it spewed out the nation that came before you. 18:29 All who do any of those toevot, such persons shall be cut off from their people. 18:30 You shall keep My charge not to engage in any of the toevot laws that were carried on before you, and you shall not defile yourselves through them: I YHWH am your God.
According to this, the practices in this list are all toevot, and they cause Israel to become impure and the land to be nauseous and vomit them out. It stresses that by abstaining from these practices the Israelites must distinguish themselves from the previous inhabitants. Why, then, is only male homosexual congress singled out with this word? Is there something more toevah about it than incest? If so, it is unclear what.
Perhaps its usage in other biblical contexts can shed light on its meaning. In Deuteronomy, for instance, the term is used to refer to idolatry (12:31; 13:15), false weights (25:13–16), transvestism (22:5) and remarrying a divorced wife (24:4). This broader scope of toevah in Deuteronomy is consistent with the more general use of this term in the book of Proverbs, where it applies to false weights (Prov 11:1; 20:10, 23), antisocial behavior (6:16–19) and distorting judgment (17:15) to name a few. For this reason, scholars have argued that Deuteronomy is building on traditions of wisdom sayings.
In the book of Ezekiel, the term is used primarily in relation to idolatry (5:11; 7:20; 11:18) and sexual misconduct (22:11). In comparison, its usage in Leviticus is the most restricted, focusing exclusively on the latter. Despite these differences, all of these sources agree that toevah refers to a behavior that is “abhorrent” or “disgusting.” In other words, the term does not seem to have a precise connotation, and a given sin’s “toevah-ness” is in the eyes of the beholder.
Another term that appears in both lists is zimmah, in this case, in reference to sexual relations with a woman and her daughter or granddaughter:
ויקרא יח:יז עֶרְוַת אִשָּׁה וּבִתָּהּ לֹא תְגַלֵּה אֶת בַּת בְּנָהּ וְאֶת בַּת בִּתָּהּ לֹא תִקַּח לְגַלּוֹת עֶרְוָתָהּ שַׁאֲרָה הֵנָּה זִמָּה הִוא.
Lev 18:17 Do not uncover the nakedness of a woman and her daughter; nor shall you marry her son’s daughter or her daughter’s daughter and uncover her nakedness: they are flesh-relations; it is zimmah.
ויקרא כ:יד וְאִישׁ אֲשֶׁר יִקַּח אֶת אִשָּׁה וְאֶת אִמָּהּ זִמָּה הִוא בָּאֵשׁ יִשְׂרְפוּ אֹתוֹ וְאֶתְהֶן וְלֹא תִהְיֶה זִמָּה בְּתוֹכְכֶם.
Lev 20:14 If a man marries a woman and her mother, it is zimmah; both he and they shall be put to the fire, that there be no zimmah among you.
The term zimmah derives from the root ז.מ.מ, a well-attested root in the Hebrew Bible meaning “to plot” (Gen 11:6; Deut 19:19). Despite this seemingly straightforward etymology, the vast majority of the appearances of zimmah pertain to sexual sins which lack any obvious connection to schemes or plotting.
The fact that zimmah refers to the same violation in both lists might suggest that this term was chosen for a precise technical nuance. However, such a conclusion is doubtful, since elsewhere it refers to other prohibitions. For example, in Leviticus 19, the chapter in between both lists, it refers to prostituting one’s daughter:
ויקרא יט:כט אַל תְּחַלֵּל אֶת בִּתְּךָ לְהַזְנוֹתָהּ וְלֹא תִזְנֶה הָאָרֶץ וּמָלְאָה הָאָרֶץ זִמָּה.
Lev 19:29 Do not degrade your daughter and make her a harlot, lest the land fall into harlotry and the land be filled with zimmah.
In Judges, in the story of the concubine in Gibeah, it is a reference to violent gang rape:
שופטים כ:ו ...כִּי עָשׂוּ זִמָּה וּנְבָלָה בְּיִשְׂרָאֵל.
Judg 20:6 …For a zimmah and nevalah (act of depravity) had been committed in Israel.
Nevalah is yet another general term for despicable acts, used elsewhere also in reference to rape (Genesis 34:7; 2 Samuel 12). It is not used in either of the lists in Leviticus, but here it appears as part of a hendiadys with zimmah, implying that they mean more or less the same thing.
A strong argument for the fluidity of the term zimmah comes from a verse in Ezekiel, which uses it in the context of sex with a daughter-in-law:
יחזקאל כב:יא וְאִישׁ אֶת אֵשֶׁת רֵעֵהוּ עָשָׂה תּוֹעֵבָה וְאִישׁ אֶת כַּלָּתוֹ טִמֵּא בְזִמָּה וְאִישׁ אֶת אֲחֹתוֹ בַת אָבִיו עִנָּה בָךְ.
Ezek 22:11 They have committed toevah with other men's wives; in their zimmah they have defiled their own daughters-in-law; in you they have degraded (ʿinna) their own sisters, daughters of their fathers.
While the usage of these terms shares with Leviticus the general reference to illicit sexual behaviors, it employs them in reference to different specific prohibitions. In Leviticus, zimmah refers to sex with a mother and daughter and toevah to male homosexual congress, while in Ezekiel 23:11 zimmah describes sex with one’s daughter-in-law and toevah adultery. This variability casts doubt on giving a strict technical sense to these terms. Moreover, in Ezekiel 23 (vv. 27, 35, 44) and in Jeremiah 13:27, the term refers to promiscuity and shameful sexual conduct in general, not to a specific prohibition.
Still, the fact that Leviticus 18 and 20 use both this term and toevah in reference to identical or near identical prohibitions might appear to support the assumption of a precise technical usage. However, in light of the objections raised above, this consistency may, perhaps, be better explained by literary dependency of one source on the other—or both on an earlier source.
Perhaps the most enigmatic of the terms is חֶסֶד (chesed), which appears only in the list in Leviticus 20 in relation to sibling incest:
ויקרא כ:יז וְאִישׁ אֲשֶׁר יִקַּח אֶת אֲחֹתוֹ בַּת אָבִיו אוֹ בַת אִמּוֹ וְרָאָה אֶת עֶרְוָתָהּ וְהִיא תִרְאֶה אֶת עֶרְוָתוֹ חֶסֶד הוּא וְנִכְרְתוּ לְעֵינֵי בְּנֵי עַמָּם עֶרְוַת אֲחֹתוֹ גִּלָּה עֲוֹנוֹ יִשָּׂא.
Lev 20:17 If a man marries his sister, the daughter of either his father or his mother, so that he sees her nakedness and she sees his nakedness, it is a chesed; they shall be excommunicated in the sight of their kinsfolk. He has uncovered the nakedness of his sister, he shall bear his guilt.
In most contexts, the word chesed means “kindness.” The term here is apparently a homonym, meaning something like disgrace. A similar use of this root as a verb seems to be attested in Proverbs:
משלי כה:ט רִיבְךָ רִיב אֶת רֵעֶךָ וְסוֹד אַחֵר אַל תְּגָל. כה:י פֶּן יְחַסֶּדְךָ שֹׁמֵעַ וְדִבָּתְךָ לֹא תָשׁוּב.
Prov 25:9 Defend your right against your fellow, but do not give away the secrets of another, 25:10 lest he who hears it bring chesed upon you, and your bad repute never end.
Similarly, in another verse in Proverbs, the term seems to have the connotation of sin or iniquity, as it is presented as the opposite of righteousness:
משלי יד:לד צְדָקָה תְרוֹמֵם גּוֹי וְחֶסֶד לְאֻמִּים חַטָּאת.
Prov 14:34 Righteousness exalts a nation, but sin is a chesed to a people.
Nevertheless, it remains unclear why incest with a sister of all sins should be referred to in this way.
The final derogatory term is tevel, which is used on both lists, but, referring to different sins:
ויקרא יח:כג וּבְכָל בְּהֵמָה לֹא תִתֵּן שְׁכָבְתְּךָ לְטָמְאָה בָהּ וְאִשָּׁה לֹא תַעֲמֹד לִפְנֵי בְהֵמָה לְרִבְעָהּ תֶּבֶל הוּא.
Lev 18:23 Do not have carnal relations with any beast and defile yourself thereby; and let no woman lend herself to a beast to mate with it; it is tevel.
A promising etymology for this word derives it from the root ב.ל.ל “mix,” offering a fitting condemnation of a sexual act that involves an act of inter-species mating as per the first list in Leviticus 18. Yet, this explanation falls flat upon the second appearance of the term:
ויקרא כ:יב וְאִישׁ אֲשֶׁר יִשְׁכַּב אֶת כַּלָּתוֹ מוֹת יוּמְתוּ שְׁנֵיהֶם תֶּבֶל עָשׂוּ דְּמֵיהֶם בָּם.
Lev 20:12 If a man lies with his daughter-in-law, both of them shall be put to death; they have committed a tevel—their bloodguilt is upon them.
Here the reference is to sexual relations between a man and his daughter-in-law. One is hard pressed to see why this latter law is any more of a mixture than the other incestuous relations. Moreover, as noted above, this particular sin is referred to as zimmah in Ezekiel 22:21.
In trying to assess whether there is a specific semantic meaning to the various terms of condemnation in Leviticus 18 and 20, it is worth comparing the first part of the incest laws in Leviticus 18 (verses 7–17), which uses a different type of rationale. Instead of words of condemnation, these verses merely restate the blood relation. For example, verse 15 reads:
ויקרא יח:טו עֶרְוַת כַּלָּתְךָ לֹא תְגַלֵּה אֵשֶׁת בִּנְךָ הִוא לֹא תְגַלֶּה עֶרְוָתָהּ.
Lev 18:15 Do not uncover the nakedness of your daughter-in-law: she is your son’s wife; you shall not uncover her nakedness.
The motive clause “she is your son’s wife” does not add any new information that wasn’t already known from the designation “daughter-in-law.” It does, however, call the listener’s attention to the fact that what may appear as a distant relation (your daughter-in-law) is in fact close – your son’s wife. This is the dominant form of explanation in vv. 7–17 for what is wrong with acting in this way, e.g. “she is your sister” (11), “she is your mother’s flesh” (13), etc. These clauses do not provide explanations but rather serve to emphasize why a certain relation is incestuous.
The important point for our purposes is as follows: by emphasizing that one’s half-sister should be viewed as equivalent to one’s sister regarding incest, for instance, the text does not bother to explain why the latter is beyond the pale. These rules take for granted that the audience should know that these acts are despicable. In the same way, the terms of condemnation referenced above should be viewed as adding rhetorical emphasis, but not as explanations. (This is in contrast to the Hittite term ḫurkel, which has a specific legal connotation; see appendix.)
A Natural Basis for Incest Avoidance?
At first glance, this negative conclusion may appear disappointing. Upon further consideration, however, it allows us to situate the biblical attitudes towards sexual taboos in relation to a fundamental dispute regarding the nature of incest prohibitions: Sigmund Freud versus Edvard Westermarck. These two thinkers were contemporaries and their exchanges in published works are well known to anthropologists.
Freud: Repression of Desire
According to Freud, the incest prohibition is a classic example of repression, with society imposing its norms on individuals, who in their natural state would be inclined to incest, specifically boys with their mothers and daughters with their fathers. In Totem and Taboo (1913), he approvingly provides the following quote from James Frazer, the early Scottish anthropologist and folklorist, best-known for his Golden Bough:
The law only forbids men to do what their instincts incline them to do; what nature itself prohibits and punishes it would be superfluous for the law to prohibit and punish. Accordingly we may always safely assume that crimes forbidden by law are crimes which many men have a natural propensity to commit. If there were no such propensity there would be no such crimes, and if no such crimes were committed, what need to forbid them? Instead of assuming therefore, from the legal prohibition of incest, that there is a natural aversion to incest we ought rather to assume that there is a natural instinct in favour of it, and that if the law represses it, it does so because civilized men have come to the conclusion that the satisfaction of these natural instincts is detrimental to the general interests of society.
Numerous statements in Talmudic literature express a similar view, for example that the Israelites cried when they heard the incest restrictions (see Rashi, Num 11:10). 
Westermarck: Innate Aversion
The opposing perspective was represented by Edvard Westermarck. In his view, humans were naturally inclined to avoid incest and thus this innate aversion was the basis for social disapproval, codified as legal prohibitions. He argued that it was improbable that laws would be able to change natural inclinations:
Even if social prohibitions might prevent unions between the nearest relatives, they could not prevent the desire for such unions. The sexual instinct can hardly be changed by prescriptions; I doubt whether all laws against homosexual intercourse, even the most draconic, have ever been able to extinguish the peculiar desire of anyone born with homosexual tendencies.
He further postulated what has since been termed the Westermarck Effect: “Generally speaking, there is a remarkable absence of erotic feelings between persons living very closely together from childhood.” A vote in favor of Westermarck’s view comes from nonhuman primates, for whom incestuous couplings between maternal relatives are rare, even under experimental conditions that would encourage such behavior.
What about Leviticus? The fact that the text brings condemnations but not rationales reveals its presumption that the immorality of the sexual taboos is self-explanatory.
Self-Explanatory Taboos: Incest and Unclean Animals
The unnaturalness of the tabooed sex acts is expressed clearly by the closing exhortation of Leviticus 20 that uses the language of Leviticus 11 with regard to pure and impure animals:
ויקרא כ:כג וְלֹא תֵלְכוּ בְּחֻקֹּת הַגּוֹי אֲשֶׁר אֲנִי מְשַׁלֵּחַ מִפְּנֵיכֶם כִּי אֶת כָּל אֵלֶּה עָשׂוּ וָאָקֻץ בָּם... כ:כה וְהִבְדַּלְתֶּם בֵּין הַבְּהֵמָה הַטְּהֹרָה לַטְּמֵאָה וּבֵין הָעוֹף הַטָּמֵא לַטָּהֹר וְלֹא תְשַׁקְּצוּ אֶת נַפְשֹׁתֵיכֶם בַּבְּהֵמָה וּבָעוֹף וּבְכֹל אֲשֶׁר תִּרְמֹשׂ הָאֲדָמָה אֲשֶׁר הִבְדַּלְתִּי לָכֶם לְטַמֵּא.
Lev 20:23 You shall not follow the practices of the nation that I am driving out before you. For it is because they did all these things that I abhorred them… 20:25 So you shall set apart the pure animal from the impure, the impure bird from the pure. You shall not make your souls disgusting through beast or bird or anything with which the ground teems, which I have set apart for you to treat as impure.
Chapter 11’s systemic categorization of the animal world is the most analogous text to the list of forbidden sexual relations in Leviticus 18 and 20. Through this allusion to the laws of impure animals, Leviticus 20 impresses on its audience the message that just as the distinction between clean and unclean is natural and embedded in the world order, so too, are the forbidden sexual relations.
A further implication is that the desire for these relations is unnatural, making the violation of these prohibitions all the more perverse. One might compare the Talmudic statement that לא נחשדו ישראל על משכב זכור ולא על הבהמה “Israel is not suspected of male homosexuality or bestiality,” which treats these proclivities as perverse and foreign to Israel.
This line of argumentation (or perhaps, non-argumentation) poses a challenge to modern readers who no longer view homosexual orientation as a choice. The present essay is not the place to try and resolve this complex theological and moral issue. Let me conclude by stressing that it is not sufficient to deal with the practical implications of biblical laws without also attempting to grapple with the underlying attitudes and moral foundations that they express.
Hittite Terms: Natta Haratar vs. Ḫurkel
A comparison to the sexual prohibitions presented in in the Hittite Laws (17th/16th century B.C.E.)—the most similar set of such laws in the ANE to those found in Leviticus—highlights the non-specific and non-legalistic usage of these terms in the Bible .
In classifying the behaviors, it employs a terminological dichotomy between proscribed and tolerated acts. The first category, consisting of severe prohibitions (for example, sexual relations with one’s mother), is labelled ḫḫurkel, a term whose etymology is unclear but seems to have the force of “abomination” in English. The second expression is more straightforward linguistically: natta haratar means “not a prohibition” and refers to acts which seem to have been deemed inappropriate but not incurring legal liability.
Thus, for example, the Hittite laws state:
- 190 …If a man has sexual relations with his stepmother, it is not an offense. But if his father is still living, it is ḫurkel.
- 191 If a free man sleeps with free sisters (i.e., not slaves) who have the same mother and with their mother—one is one country and the other in another, it is not an offense. But if it happens in the same location, and he knows of the relationship, it is ḫurkel.
Through this dichotomy, these terms produce a clear functional distinction: Forbidden sexual acts are ḫurkel. In comparison, the alternation of terms in Leviticus appears eclectic, as does the fact that many of the prohibited acts receive no term at all. It thus seems clear that the terms play a rhetorical rather than strictly legal function.
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Dr. Yitzhaq Feder is a lecturer at the University of Haifa. He is the author of Blood Expiation in Hittite and Biblical Ritual: Origins, Context and Meaning (Society of Biblical Literature, 2011). His upcoming book, Contagion and Cognition: Defilement as Embodied Discourse in the Hebrew Bible, examines the psychological foundations of impurity in ancient Israel.
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