18:1–2 The incest laws are introduced with the very same words that introduce the covenant: “I am the Lord your God” (Ex. 20:2; Deut. 5:6).212 The well-known statement links these laws to Israel’s deliverance from Egypt, which made them God’s very own people. It frames Israel’s obedience as allegiance to their Sovereign, whose moral authority stands behind these prohibitions. Evoking the covenant of Sinai is especially fitting for laws that deal with the covenant of marriage.

18:3–4 The exhortation not to conform to the practices of the nations comes at both the beginning and the end of the chapter, forming an envelope around prohibited sexual practices (Lev. 8:2, 4, 5, 30). Having left Egypt behind and setting its sights toward Canaan, Israel is urged to neither look back nor embrace the customs of where it is going, but to look to the holy God who dwells in its midst and to conform to his character. His people are to live as a people set apart to him—in the world but not of it (20:26; John 17:15–16).

By associating disordered sexual behavior with Egyptians and Canaanites the law effectively defines sexual sins as “foreign” to the people of God.213 Israel is called to be a holy people who do “not walk in their statutes” (Lev. 18:3), for the Israelites have bound themselves by covenant to walk in the Lord’s (v. 4). Although the world competes for their allegiance and affection, they must demonstrate their covenant commitment by pursuing God’s righteousness with their bodies, in worship (chs. 1–16) and in ethical living (chs. 17–27).

18:5 These laws are ordained by God and lead to life. The reward for obedience is life; the consequence of disobedience is delayed until the end of the chapter (vv. 24–30). Life is built into the commands because they keep Israel in right relationship with the Lord who is Life himself. The Lord will uphold those who walk in obedience and cause them to flourish (26:9, 11–12). By walking in his ways they will enjoy life in the land and not be expelled, like the nations before them were (18:24–30; Deut. 5:33). Life will work its way into their families as they renounce practices that betray marriage’s sacred trust, violate the vulnerable, and hinder life’s potentiality through unions that are not fruit bearing.

18:6 This verse is an introduction to the incest laws, which prohibit sexual relations with “close relatives,” which in biblical thought includes relatives by blood (Lev. 18:7, 9, 10, 12, 13) or marriage (vv. 8, 11, 14, 15–17). The Hebrew expression is two nearly identical words: basar sheʾer (“flesh of [his] flesh”). Becoming one flesh is the bond of a new family unit.214 Flesh defines family.215

The laws are given from the perspective of the male head of family, whose household includes two to three generations of blood kin as well as family by marriage (vv. 8, 15–18). The “father’s household” (bet ʾab) includes his wife, married sons and their wives, unmarried daughters, and unmarried female blood relatives, such as a widowed mother, aunts, and sisters. Young women who marry into the household become “flesh family” through marriage. Close kin is spoken of as sharing the same flesh and bone, as Laban declares to his nephew Jacob, “Surely you are my bone and my flesh!” (Gen. 29:14; cf. Gen. 37:27; 2 Sam. 5:1).

Every Israelite has formal responsibilities toward his flesh family: to protect and provide (Ruth 2:20; 4:1–6), redeem from debt slavery (Lev. 25:47–55), redeem ancestral inheritance (25:23–25; Jeremiah 32), provide an heir to continue lineage (Deut. 25:5–10), pass down knowledge of God’s saving acts (Ps. 78:5–7), provide proper burial (2 Sam. 21:8–14), and even avenge murder (Num. 35:19).

It is also his responsibility not to engage in illicit sexual relations by uncovering or revealing a woman’s nakedness (Lev. 18:7–16). Sexual intimacy is more commonly expressed as “to lie with”216 or “to know”217 someone. The phrase “to uncover one’s nakedness” is used of prohibited sexual relations in which there is sexual vulnerability, exposure, and shame.218 This is in stark contrast with nudity in marriage, through which there is a mutual vulnerability with no shame (Gen. 2:25).

Whose nakedness is being exposed? Most of the time it is the woman’s own (Lev. 18:9, 11, 15, 17, 18, 19), while at other times it is an offense against the man who is in a marriage covenant, with exclusive conjugal rights to his wife’s sexuality (vv. 8, 16). The prohibitions are not worded as a husband’s rights to his wife’s body, as though she were property (to the contrary cf. v. 19), but rather they locate the proper union for sharing holy intimacy. By prohibiting a whole web of sexual relations the law protects the sexual union of a husband and wife, guarding the sanctity of marriage.219

18:7 Sexual transgressions against one’s father and mother are strictly prohibited, something that is universal in all human culture. The prohibition is stated as protecting the right of a husband’s access to his wife’s sexuality, covenanted exclusively to him. A mother’s nakedness is equated with a father’s nakedness, since they belong to one another. A husband and wife are one flesh through the bonds of marriage, and thus to expose her is to expose him.

18:8 Sexual relations are forbidden with the wives of one’s father, whether secondary wives or those married after a mother’s death, because they violate the father’s conjugal rights. Reuben, Jacob’s firstborn, violated his father’s rights by having sexual relations with Bilhah, his father’s concubine (Gen. 35:22; 49:3–4). The act challenged his father’s authority and leadership of the family (also 2 Sam. 16:21–22). Reuben forfeited his birthright as a result (1 Chron. 5:1). The penalty is prescribed in Leviticus 20:11.

18:9 Sisters and half-sisters (born to one’s father or mother by another union) are protected from sexual advances. Whether raised in the same family household or another, sisters are off limits.220 The law is binding even when they do not live in proximity. Instead an Israelite male bears responsibility to protect and provide for his unmarried or widowed sister (21:3), and custom demanded that he even avenge her honor, as do Jacob’s sons for their sister, Dinah, (Genesis 34) and Absalom for Tamar (2 Sam. 13:20).221 The penalty is prescribed in Leviticus 20:17.

18:10 A male head of the household may not approach his granddaughter sexually. The explanation that “their nakedness is your own nakedness” refers to shared blood ties. A granddaughter (and implicitly a daughter) is one’s own flesh and blood. It is a man’s responsibility to bless, protect, and pass down the faith to his children and his “children’s children” (Gen. 48:8–16; Deut. 4:9–10).

18:11 Sexual relations with one’s half-sister born of another mother (concubine) are forbidden. The stepsister is to be treated as a natural-born sister, meaning she has entered the household to be provided for and protected. She is accorded full status as a sister.

18:12–13 Aunts from either side of the family are protected from sexual advances because they are a father’s or mother’s own flesh relations. The balanced prohibitions from both sides of the family respect the ties forged between the two households through marriage. A family’s strength comes from the loyalty of its relationships. The penalty is prescribed in 20:19.

18:14 Adultery with a paternal uncle’s wife offends an uncle’s sexual rights by marriage covenant. His wife has become one’s aunt through marriage. The penalty is prescribed in 20:20.

18:15 A daughter-in-law who has come into the household of her husband is protected from sexual advances of other men in the family even after his death (cf. 18:8). The law upholds a son’s rights and sets limits for the family’s patriarch. Heads of households do not have rights to the women of their extended family but rather are charged to care for and protect them (Ruth 2:9). Marriage creates kinship ties and alliances between families. The penalty is prescribed in Leviticus 20:12.

Judah’s obligation toward Tamar, which he was lax in fulfilling, led to the breach of this prohibition (Gen. 38:13–26). Tamar is praised for her loyalty in protecting her deceased husband’s rights to an heir by crossing boundaries to bear a son who would legitimately continue his lineage.

18:16 It would be dishonorable to both one’s brother and his wife to make sexual advances toward a sister-in-law. It would not only degrade his wife but also confuse family inheritance. In the case of a brother’s death his widowed wife is protected from abuse. She is not treated as property that passes among brothers. The penalty is prescribed in 20:21.

A different passage deals with one’s responsibility toward a brother’s widowed wife if she has no sons. A man whose brother has died with no heirs is to take his brother’s place. He weds his sister-in-law to produce an heir so that his brother’s lineage and share in the family estate are not lost (Deut. 25:5–10). To perpetuate his name and memory is to allow him to live on through his descendants. The arrangement provides security for the widow in a legitimate relationship (Ruth 1:9).

18:17 This law protects the rights of a wife by guarding the covenant union of marriage. It implicitly prohibits incest with one’s daughter as legislated from the perspective of his wife. A woman’s female descendants, her daughters and granddaughters, are never permitted as potential partners. The law protects not only the daughters but, importantly, also the bond between mother and child by not making a daughter equal in the relationship. God judges this as depravity (Hb. zimmah), a word used of such acts as forcing a daughter into prostitution or the rape of the Levite’s concubine (Judg. 20:6). The penalty is prescribed in Leviticus 20:14.

18:18 This law may be taken as preventing the marriage of biological sisters or, taking the word “sister” more broadly, as outlawing polygamy.222 It bridges the laws of forbidden sexual unions within the family (vv. 6–17) and those of other forbidden sexual practices (vv. 19–23). If the word “sister” is taken strictly, the law protects a wife’s honor with respect to her own female blood relatives. If the word “sister” is understood more broadly, the law protects the bonds of loyalty and intimacy between a husband and wife that a rival would compromise. Biblical narratives of polygamy paint the anguish of women’s vying for their husband’s affection in competition for children (Gen. 16:5; 21:10; 30:1–24; 1 Samuel 1). The Lord’s ordering of relationships restores peace to family dynamics threatened by the fall.

18:19 Even within God-ordained sexual unions there are boundaries to conjugal rights: a husband may not pursue sexual relations with his wife during her menstrual impurity (Lev. 12:2, 5). This law recognizes that, though husband and wife belong to each other, ultimate authority over a woman’s body is the Lord’s (1 Cor. 7:3–5). Mutuality and respect are understood by this ruling. The penalty is prescribed in Leviticus 20:18.

18:20 Marital fidelity is the foundation of the marriage covenant, guarded by the Decalogue (Ex. 20:14; Deut. 5:18). Adultery is defined as sexual relations with a woman who is married or betrothed (Deut. 22:22–24). Sexual relations are powerful, creating physical, emotional, and relational bonds. In the wrong context, however, such relations destroy already existing bonds to forge new ones that threaten marriage, family, and society. Children conceived from the union are on the margins (Deut. 23:2; Judg. 11:1–3). Disordered sexual practices are disordering and result in moral defilement.223 Jesus gets to the heart of adultery by locating it not only in the physical act but also in its contemplation (Matt. 5:27–28). The penalty is prescribed in Leviticus 20:10.

18:21 Child sacrifice is included in these laws because children are the fruit of sexual union. This verse is linked to the previous one by the keyword “seed” (Hb. zeraʿ), referring to semen or offspring. Those who participate in the pagan practice of giving their children to Molech profane the name of Yahweh (19:12; 20:3). To profane or make common is to tarnish the Lord’s reputation and make him appear as the gods of the nations. The penalty is prescribed in 20:2.

18:22 Homosexuality is prohibited as a violation of God’s creational design. Man (Hb. ʾish) and woman (ʾishah) belong together, as much as their names share a fundamental unity. The phrase to “lie . . . as with a woman” already implicitly communicates that a man belongs with a woman. Substituting a male for a female and sexually behaving as though a man were a woman is a union the Lord neither intended nor blessed at creation.

Homosexuality is called an “abomination” (toʿebah), as are all prohibited sexual practices in this chapter (vv. 26, 27, 29, 30). Yet this is the only one individually labeled as such. Hebrew toʿebah is used for that which is wholly incompatible with God’s character and, as Crouch observes, refers particularly to the “delineation and protection of boundaries.”224 This is a nonnegotiable boundary for the Israelites, who are urged to avoid behaviors that must never define God’s people. Israel must keep separate from the practices of the nations in order to remain united with the Lord.

The phrasing of this law continues the legal pattern of addressing the male head of household but would apply naturally to women as well. Lesbianism is explicitly condemned in the NT (Rom. 1:26). The penalty is prescribed in Leviticus 20:13.

18:23 Bestiality involves a different violation of creational boundaries. According to the Lord’s design animals are to mate and reproduce after their own kind. Only a human being can ever be a suitable covenant partner and life companion for another human being (Gen. 1:24–31; 2:20). This prohibition speaks volumes to the nature of humanity. Although created on the sixth day alongside other living beings, a human is not a more sophisticated animal but a unique creation in the very image and likeness of God. Human sexual intimacy is a gift dignified and blessed by God and quite unlike the animalistic drive to mate. To engage sexually with an animal is “perversion” (Hb. tebel), an expression that points to a confusion of categories.225 It is disordered sexuality. The verse begins by addressing men and then makes explicit that the law applies also to women. The penalty is prescribed in Leviticus 20:15–16.

18:24–25 The chapter ends with a threat of expulsion that recalls the expulsion from the garden (Gen. 3:23–24). As it makes ready to enter the land, Israel is reminded that the nations are being evicted because of their sexual immorality. The Lord is the divine householder entrusting the land into Israel’s care as its share of the paternal estate. The land must be treated as holy because the Lord himself inhabits it among his covenant family and from this promised plot extends his reign throughout the earth (Ex. 15:17).

A rightly ordered sexual ethic is critical to preventing uncleanness that would cause the people to forfeit their inheritance.226 Like a mirror, the land reflects Israel’s standing with its heavenly Father. If God’s people live by his commandments and conform to his character, they will remain secure in the land; if they neglect his commands and conform to the practices of the nations, they will be evicted.

18:26 The resident alien will be held accountable for practices that defile the land. Under godly covenant stewardship the land will sustain both native and resident alien. While resident aliens cannot permanently own the land deeded to Abraham’s descendants,227 their poor can glean from the land’s yield to satisfy their hunger (19:10; 23:22).

18:27–30 As covenant witness, the land will testify against the moral impurity within it (Deut. 30:19; Isa. 24:4–5). The land is personified, taking on human qualities to express disgust at its defilement and pollution. The word for “land” is grammatically feminine in Hebrew, painting the striking image of a woman who is retching at the sexual sin perpetrated against her. In disgust she vomits out her violators until she can have rest from wrongdoing (Lev. 26:34–35).

Israel’s election is an act of God’s grace. He takes them as his people by covenant and invites them into a dynamic relationship wherein they participate in their sanctification. The privilege of election carries with it the obligation of obedience in order to avoid defiling ways. The Lord is not judging the nations because of their ethnicity but holding them accountable for their sin (Gen. 15:16). Should Israel stray from his life-giving laws, she will deserve the same.