Leviticus 18
The Holiness Code begins with the sexual ethics that distinguish the covenant community from both Egypt (the culture they left) and Canaan (the culture they are entering). The chapter opens with the covenant formula — I am the Lord your God — and frames the regulations negatively (not as Egypt, not as Canaan) and positively (keep my decrees and laws, for the person who obeys them will live by them). The prohibited relationships cover the full range of incest (parents, step-parents, grandchildren, step- and half-siblings, aunts, uncles, aunts-by-marriage, daughters-in-law, sisters-in-law), adultery, the wife's sister during the wife's lifetime, menstrual impurity, child sacrifice to Molek, male same-sex intercourse, and bestiality. The theological rationale is the land's defilement: the Canaanites practiced these things, and the land vomited them out; if Israel practices the same things, the land will vomit out Israel. The chapter closes with the I am the Lord your God formula that opened it, grounding every ethical requirement in the covenant's identity rather than merely in social utility or natural law.
Leviticus 18:23
Do not have sexual relations with an animal and defile yourself with it. A woman must not present herself to an animal to have sexual relations with it; that is a perversion. The prohibition on bestiality — both for men and for women — is called a perversion — tevel, a confusion or mixing that violates proper categories. The dual prohibition (for men and for women) communicates the comprehensive nature of the covenant's sexual ethics: the protection of proper sexual categories applies equally to both sexes.
Leviticus 18:1
The Lord said to Moses. The sexual ethics regulations of Leviticus 18 open the Holiness Code — the section of Leviticus (chapters 18–27) that applies the holiness of God to the practical and social life of the covenant community. The shift from the ritual regulations of chapters 1–17 to the ethical and social regulations of chapters 18–27 communicates that holiness is not only expressed in the sanctuary's rituals but in the community's daily relationships and behavior. I am the Lord your God is the grounding formula that will punctuate the holiness code throughout: the ethical requirements are grounded in the identity of the God who makes them.
Leviticus 18:2
Speak to the Israelites and say to them: I am the Lord your God. The self-identification of God as the Lord your God precedes every regulation in the Holiness Code. The regulations that follow are not arbitrary restrictions but expressions of the character of the God who has identified himself as Israel's God. The covenant relationship — I am the Lord your God — is the foundation of every ethical requirement that follows. The same formula that introduced the Ten Commandments (Exodus 20:2) introduces the Holiness Code's application: the identity of God grounds the obligations of the covenant community.