Do Not Have Relations with Your Daughter-in-Law
The Daughter-in-Law — The Talmud’s Paradigm Case
Leviticus 18:15: “Do not have sexual relations with your daughter-in-law. She is your son’s wife; do not have relations with her.” The verse is unusually emphatic — the prohibition stated twice in a single verse. The Talmud (Sanhedrin 54b) cites the daughter-in-law case as the paradigm of illicit relations: the one from which all other forbidden unions are analogically derived. The double statement reflects the severity of the violation: the father-in-law and son’s wife combination disrupts the family from two directions simultaneously — the father’s authority over his son’s household, and the son’s trust in his father.
Unlike the aunt (#365) and uncle’s wife (#366), the daughter-in-law is related to the prohibiting party only through her marriage to the son. She is not a blood relative. But the Torah treats this as irrelevant — the marriage bond between the son and his wife creates a relational domain that the father may not enter, precisely because the bond between the son and his wife is the direct product of the father’s household.
Judah and Tamar — The Paradigm Violation
Genesis 38:1–26: Tamar was the wife of Er, Judah’s firstborn. Er died (Gen 38:7). Tamar then became the wife of Onan through levirate obligation. Onan also died (Gen 38:10). Judah sent Tamar back to her father’s house to wait for his third son Shelah, then forgot the promise (Gen 38:14). Tamar disguised herself as a prostitute and sat at the road to Enaim, where Judah passed and, not recognizing her, hired her. She became pregnant.
When Tamar’s pregnancy became known, Judah ordered her burned: “Bring her out, and let her be burned” (Gen 38:24). Tamar then produced the seal and cord she had taken from Judah as pledge, and Judah recognized them: Genesis 38:26: “Then Judah identified them and said, ‘She is more righteous than I, since I did not give her to my son Shelah.’” Judah confessed his own guilt — not that he had slept with his daughter-in-law, but that his withholding of Shelah had driven Tamar to this act. The Torah records his acknowledgment of moral culpability. The twins Perez and Zerah, born of this union, become ancestors of the Davidic line. The story does not endorse the violation but records the complex moral accountability within it.
The Double Bond — Father, Son, and the Trust Between Them
The rabbis (Yevamot 21a) note that commandment #367 is violated even after the son’s death — the daughter-in-law remains forbidden to the father-in-law permanently, unlike the situation where a widow might typically be free to remarry. Once she has been the son’s wife, the relational domain is fixed: she is forever the son’s wife, even if he is no longer living.
The prohibition protects the integrity of the father-son relationship at the most intimate level. Leviticus 18:29–30: those who violate these prohibitions face karet — being cut off from the people. The language of being cut off reflects a severing from the covenant community, a rupture of the relational network that the covenant is designed to maintain. The father who violates his son’s wife has not merely committed a sexual act; he has severed the trust that makes family structures function.
- Judah and Tamar — Gen 38:1–26: the Torah’s own story of the daughter-in-law violation. Judah slept with Tamar unknowingly; when confronted, he said “She is more righteous than I.” The twins born, Perez and Zerah, became ancestors of the Davidic line.
- Er and Onan — Gen 38:7–10: both died, leaving Tamar a widow awaiting Shelah. Their deaths created the situation Judah failed to resolve, leading to Tamar’s desperate act. Their deaths frame the backdrop of the prohibition’s most famous narrative.
- Perez — Gen 38:29: born of the Judah-Tamar union; ancestor of Boaz, David, and ultimately the Davidic dynasty. The Torah records this lineage without concealment. Matthew 1:3 includes both Judah and Tamar explicitly in the genealogy.
Read the source passage in the Torah reader.
Read in the Torah Reader — Leviticus 18:15