What Does the Bible Say About Incest?

TL;DR: The Bible explicitly condemns incest in multiple passages, particularly in Deuteronomy, where specific family relationships are named and cursed. Sexual relations between close relatives — including siblings and in-laws — are treated as serious moral violations. Deuteronomy 27:22 pronounces a curse on anyone who lies with a sister Deuteronomy 27:22, and Deuteronomy 27:23 extends that curse to relations with a mother-in-law Deuteronomy 27:23. These prohibitions reflect a broader biblical ethic of sexual holiness and the protection of family boundaries.

"Cursed be he that lieth with his sister, the daughter of his father, or the daughter of his mother. And all the people shall say, Amen."

— Deuteronomy 27:22 Deuteronomy 27:22

This verse is part of a series of public covenant curses delivered by Moses to the people of Israel on Mount Ebal. The communal response — "Amen" — signals that these prohibitions carried collective moral and spiritual weight for the entire community Deuteronomy 27:22. The curse isn't merely legal; it's covenantal, meaning violation ruptures one's standing before God and community.

Deuteronomy 27:23 extends the prohibition further:

"Cursed be he that lieth with his mother in law. And all the people shall say, Amen."

Deuteronomy 27:23 This shows that the biblical concern isn't limited to blood relations alone — it encompasses the broader family structure created through marriage. Together, these passages establish that incest, in its various forms, is treated as a grave transgression in the Hebrew scriptures.

Protestant · Christianity

Protestant View on Incest

"Cursed be he that lieth with his sister, the daughter of his father, or the daughter of his mother. And all the people shall say, Amen."

Protestant Christianity has historically grounded its sexual ethics firmly in Old Testament law as interpreted through the lens of the New Testament's moral continuity. The explicit curses in Deuteronomy 27 are understood not merely as ceremonial or civil laws unique to ancient Israel, but as expressions of God's enduring moral order Deuteronomy 27:22 Deuteronomy 27:23.

Deuteronomy 27:22 names the specific sin of lying with a sister — whether she is the daughter of one's father or one's mother — and declares it cursed before the entire assembly Deuteronomy 27:22. Protestant theologians like John Calvin and Matthew Henry understood these curses as reflecting natural law written on the conscience, meaning incest isn't just culturally prohibited but morally disordered at its root.

Protestant ethics also situates incest within the broader category of sexual immorality condemned throughout Scripture. While Deuteronomy 5:18 addresses adultery — "Neither shalt thou commit adultery" Deuteronomy 5:18 — Protestant interpreters have consistently read the Seventh Commandment as encompassing all unlawful sexual unions, including incestuous ones. The family unit is seen as a divinely ordered institution, and incest is viewed as a fundamental violation of that order Deuteronomy 27:23.

Key takeaways

Deuteronomy 27:22 explicitly curses sexual relations with a sister — whether the daughter of one's father or mother — with the entire community affirming 'Amen.' Deuteronomy 27:22
Deuteronomy 27:23 extends the biblical prohibition to include sexual relations with a mother-in-law, showing the concern covers both blood and marriage-based family ties. Deuteronomy 27:23
The Bible's condemnation of incest is covenantal and communal, not merely private — violations were considered offenses against God and the entire community. Deuteronomy 27:22
Protestant Christianity reads the Seventh Commandment's prohibition of adultery (Deuteronomy 5:18) as part of a broader sexual ethic that encompasses incest. Deuteronomy 5:18
Proverbs 6:32 warns that sexual immorality destroys one's soul, a principle Protestant interpreters apply to incestuous relationships as among the gravest violations. Proverbs 6:32

FAQs

Does the Bible explicitly name incest as a sin?

Yes. Deuteronomy 27:22 explicitly curses anyone who lies with a sister, whether she's the daughter of his father or his mother, and the entire assembly affirms it with "Amen" Deuteronomy 27:22. Deuteronomy 27:23 similarly curses relations with a mother-in-law Deuteronomy 27:23. These aren't vague moral principles — they're specific, named prohibitions embedded in Israel's covenant law.

Does the Bible's condemnation of incest include in-laws?

Yes. Deuteronomy 27:23 states, "Cursed be he that lieth with his mother in law. And all the people shall say, Amen" Deuteronomy 27:23. This shows the biblical prohibition extends beyond blood relatives to those joined through marriage, protecting the integrity of the entire family structure, not just biological lines Deuteronomy 27:22.

How does the biblical prohibition on incest relate to other sexual sins?

The Bible treats incest as part of a broader category of sexual immorality. The Seventh Commandment in Deuteronomy 5:18 prohibits adultery Deuteronomy 5:18, and Proverbs 6:32 warns that sexual immorality destroys one's soul Proverbs 6:32. Protestant tradition reads these together as a unified moral framework in which incest represents one of the most serious violations of God's design for human sexuality and family life Deuteronomy 27:22.

Is the curse on incest in Deuteronomy 27 a public or private matter?

It's explicitly public. Deuteronomy 27:22 records that "all the people shall say, Amen" after the curse is pronounced Deuteronomy 27:22, and the same communal response follows the curse on relations with a mother-in-law in Deuteronomy 27:23 Deuteronomy 27:23. This communal affirmation signals that sexual ethics, including the prohibition of incest, was a matter of collective covenant responsibility in ancient Israel.

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