Leviticus 18:6 Commentary: Incest Prohibited

The ancient Near East where Israel was forged practiced forms of incest that the Torah forbids. Clarke observes that Egypt tolerated brother-sister unions, while Jamieson-Fausset-Brown note that “great laxity prevailed amongst the Egyptians” in conjugal matters. Canaanite culture also permitted incest (the land is defiled by such acts, vv. 24, 25). God called Israel out of these nations; the laws in Leviticus 18 draw a boundary around the family as a sacred space. The phrase “none of you shall approach” (loʾ tikrevu) uses the Qal imperfect with loʾ, carrying the force of an absolute prohibition, not merely a suggestion but a command with no exceptions. The terms sheʾer and basar together suggest a kinship bond that should not be violated sexually. Clarke points out that in the world’s infancy, sibling marriage was necessary for human propagation, but once that necessity ended, the practice became “inexpedient and improper.” The law thus protects the distinct roles within a family, a man cannot simultaneously be a husband to his sister and a brother, and extends social bonds outward, strengthening the community. Calvin notes that even Roman law, “as if their authors had learnt from Moses,” codified similar degrees. Israel’s calling was to be holy as God is holy (v. 2).

The supplied commentaries and sources note no significant textual variants for Leviticus 18:6. The Hebrew text is stable across manuscripts, and the verse is not the subject of textual debate.

Leviticus 18:6 has been foundational for Christian marriage law and sexual ethics. Early church fathers like Augustine saw the prohibitions as rooted in natural law, a view echoed by Calvin who noted the parallels in Roman law. The Roman Catholic Church developed its list of prohibited degrees of consanguinity and affinity largely from this chapter. Protestant reformers such as Luther and Calvin upheld these restrictions as binding for all Christians, though some later traditions allowed marriage between cousins based on a narrower reading of “near of kin.” Jewish interpretation (Talmud, Rashi) applied the prohibition to Gentiles as well, understanding “a man, a man” to include all humanity. In modern debates, the verse is cited by Christians of all traditions to defend the sanctity of the family against incest.

Three-point outline

1. A clear boundary. The command prohibits approaching any close relative (“flesh of his flesh”) to uncover nakedness. This is a bright line protecting the family from sexual confusion.
2. A euphemism for sin. “Uncover nakedness” carries the shame of exposure (Genesis 3:7; 9:22). The language itself reminds us that such acts are not neutral; they bring disgrace.
3. A divine signature. “I am Yahweh” is not a footnote. It grounds the law in God’s character and covenant. These commands are rooted in who God is and what He has done for Israel.

Five-point outline

1. The general principle (v. 6). No sexual approach to close kin.
2. Specific applications (vv. 7, 18). Mother, step-mother, sister, granddaughter, aunt, daughter-in-law, sister-in-law, and others, each case is named.
3. Boundaries within the family. The law preserves the integrity of each relationship: parent-child, sibling, in-law.
4. Contrast with surrounding nations. Egypt and Canaan defiled themselves with incest; Israel must be different.
5. The theological motivation. Obedience flows from knowing God: “I am Yahweh your God” (v. 2). The law is a gift, not a burden.

Illustration hooks

• Fence around a dangerous cliff. The prohibition is like a fence placed not to restrict freedom but to prevent a fall. The family is a sacred space; incest destroys it.
• Shared house rules. Every household has rules that protect relationships. A father and daughter do not date; a brother does not romance his sister. God’s law formalizes what nature itself teaches.
• Map of a minefield. The specific prohibitions (vv. 7, 18) are like a map showing where the explosives are. The general command (v. 6) says: step carefully.

Questions your congregation is asking

• Why does God care so much about sexual boundaries within families?
• What about cousins? Does this law still apply, or was it for ancient Israel only?
• If early humans needed to marry siblings, why is it now forbidden?

This verse opens the section on prohibited sexual relations in Leviticus 18. It is a general command that sets the stage for specific cases. The discussion below will help your group understand the meaning of “uncover nakedness” and the rationale for the prohibition.

Discussion questions

1. What does the phrase “none of you shall approach any close relatives” suggest about the nature of the command? Is it just for Israel, or does it apply to all people?
2. Why do you think God uses the euphemism “uncover nakedness” rather than a more direct term for sexual intercourse? What does that tell us about how He views these acts?
3. Read Leviticus 18:3, 5. How do these verses help us understand why God forbids incest? What were the Egyptians and Canaanites doing?
4. The law includes step-relatives (e.g., “your father’s wife” in v. 8). Why do you think marriage to a step-mother or step-sister is forbidden? What principle is at work?
5. In Leviticus 20:11, 12 and 20:17, the consequences for incest include death or being “cut off.” Why is the penalty so severe? Does this surprise you?
6. How does the phrase “I am Yahweh” (used repeatedly in Leviticus 18) change the way you read these commands? What does it mean for God to attach His name to a law?
7. If someone says, “These are just Old Testament rules that don’t apply today,” how would you respond based on the text and its rationale?