No one is to approach any close relative to have sexual relations (18:6). Genesis recounts incest between Lot and his daughters (Gen. 19:30–38) and between Reuben and Bilhah, his father’s concubine (35:22; 49:4). Incest was common in families of Egyptian pharaohs for the purpose of concentrating power. In ancient Iran, marriages of men to their sisters, daughters, or even mothers were regarded as acts of piety.175 However, most ancient societies discouraged incest. The Babylonian Laws of Hammurabi and the Hittite Laws viewed some sexual liasons in ways that are paralleled in Leviticus 18 and 20.176 The accompanying chart basically follows the order in Leviticus 18.
Relationship to a Man: mother
Leviticus 18: forbidden
Laws of Hammurabi: forbidden
Hittite Laws: forbidden
Relationship to a Man: daughter
Leviticus 18: implicitly forbidden
Laws of Hammurabi: forbidden
Hittite Laws: forbidden
Relationship to a Man: son
Leviticus 18: implicitly forbidden
Hittite Laws: forbidden
Relationship to a Man: full sister
Leviticus 18: implicitly forbidden
Relationship to a Man: father’s wife
Leviticus 18: forbidden177
Leviticus 20: forbidden
Laws of Hammurabi: forbidden if she was the principal wife who had borne children
Hittite Laws: forbidden with step-mother only while father is alive
Relationship to a Man: half sister
Leviticus 18: forbidden
Leviticus 20: forbidden
Relationship to a Man: grandchild
Leviticus 18: forbidden
Relationship to a Man: stepsister
Leviticus 18: forbidden
Relationship to a Man: aunt
Leviticus 18: forbidden
Laws of Hammurabi: forbidden
Relationship to a Man: daughter-in-law
Leviticus 18: forbidden
Leviticus 20: forbidden
Laws of Hammurabi: forbidden
Relationship to a Man: brother’s wife
Leviticus 18: forbidden
Leviticus 20: forbidden
Hittite Laws: forbidden only while brother is alive
Relationship to a Man: woman + her daughter or mother
Leviticus 18: forbidden
Leviticus 20: forbidden
Hittite Laws: forbidden if he is married to one or the other178
Relationship to a Man: woman + her granddaughter
Leviticus 18: forbidden
Relationship to a Man: sister of wife while wife is alive
Leviticus 18: forbidden to marry
Hittite Laws: forbidden
Here are some points of comparison between Leviticus and the Hittite laws:
1. The Hittite laws explicitly label sexual relations between a man and his daughter or son “an unpermitted sexual pairing.” These cases are not specified in Leviticus but are covered, along with the case of a full sister, by the general principle that “no one is to approach any close relative to have sexual relations” (18:6).179
2. The Hittite laws forbid sexual union of a man with his brother’s wife only while his brother is alive and mandate: “If a man has a wife, and the man dies, his brother shall take his widow as wife. (If the brother dies) his father shall take her. When afterwards his father dies, his (i.e., the father’s) brother shall take the woman whom he had.”180 This is like levirate (brother-in-law) marriage in Deuteronomy 25:5–10, which is more restricted in that it applies only if the widow has no son and does not provide for the event that her brother-in-law subsequently dies. However, in Genesis 38 Tamar tricks her father-in-law into impregnating her after his son died.
3. In the Hittite laws, a man is not permitted to sexually approach his wife’s daughter. If he is married to a daughter, he may not sexually approach her mother or sister. However, “if a man’s wife dies, [he may take her] sister [as his wife.] It is not an offense.”181 This cluster of provisions would include the situation addressed in Leviticus 18:18—“Do not take your wife’s sister as a rival wife.” Some have argued that “sister” here broadly refers to any other woman, so that this is a blanket prohibition of polygamy.182 But the immediately preceding context is incest, and in the parallel Hittite legislation “sister” is obviously used narrowly and literally within the immediate family, along with “daughter” and “mother.”
4. The Hittite laws introduce a subjective element not present in Leviticus: a man’s knowledge of relationships between women. If he “sleeps with free sisters who have the same mother and with their mother—one in one country and the other in another, it is not an offense.” But if this occurs in the same place and he knows that the women are related, “it is an unpermitted sexual pairing.”183
5. Unlike Leviticus 18 and 20, the Hittite laws include permitted liaisons, cover situations in which male relatives sleep with the same woman, and address cases involving slaves or prostitutes, in which incest standards are lowered.
Do not lie with a man as one lies with a woman (18:22). This verse and 20:13 categorically and unambiguously condemn male homosexuality as an abomination to God, punishable in 20:13 by death.184 There is plenty of evidence for homosexuality and bestiality in the ancient Near East.185 A Mesopotamian omen (concerned with results rather than morality) prognosticates: “If a man has anal sex with a man of equal status—that man will be foremost among his brothers and colleagues.”186 However, the Middle Assyrian laws have a different attitude, which is closer to that of Leviticus: “If a man sodomizes his comrade and they prove the charges against him and find him guilty, they shall sodomize him and they shall turn him into a eunuch.”187 In harmony with this negative assessment, a confession of righteousness in the Egyptian Book of the Dead affirms: “I have not copulated with a boy.”188
Do not have sexual relations with an animal (18:23). Unlike the Bible, Ugaritic mythology describes bestiality by deities. For example, when Motu threatens Baʿlu (Baal) with death, the latter seeks to guarantee himself a form of afterlife through progeny by repeatedly copulating with a cow, which conceives and bears him a male.189 This is not so surprising because mixed beings were common in the realm of the gods throughout the ancient Near East.190
As with homosexuality, the Bible bans bestiality because it violates the order of sexual pairings (heterosexual within a species) that God established at creation (Gen. 1–2). The Hittite laws condemn a person who engages in bestiality with certain kinds of animals (cow, sheep, pig, dog) to death unless the king grants him mercy, which may also be extended to the animal. Even if the monarch hears his case, the offender may not personally appear before him lest the king be (secondarily) defiled.191 For the concept that illicit sexual activity defiles, compare Leviticus 18:20; Numbers 5:13, etc. (adultery), and Leviticus 18:23 (bestiality).