Does the Torah Prohibit Father–Daughter Incest?

The addressee is never the woman. So, in this case, the fact that a woman may not sleep with her husband’s son can be deduced, but the Torah never says this explicitly.

These are child sacrifice to Molech (vv. 2–5), necromancy (vv. 6, 27), cursing one’s parents (v. 9), and eating impure meats (v. 25).

The addition of the granddaughter is most likely the reason for Leviticus 18’s change of the phrasing from “a woman and her mother” to “a woman and her daughter.”

Notably, this introduces a redundancy: Any granddaughter of ego is also the granddaughter of a woman with whom ego has had sex.

This is also the reason why the very short list of prohibited relations in Deut 27:20–23 (father’s wife, half-sister and mother-in-law) only deals with secondary cases, as opposed to mother, sister, and daughter.

The same may be true of extended family and most relatives by marriage. See my discussion in “Sexual Prohibitions in the Bible and the ANE: A Comparison,” TheTorah.com (2018).

Another possible, though less probable, reason is that Leviticus 20 may have wanted to avoid redundancy. After all, the prohibitions on mother and daughter are already implicit in other laws. Notably, while Leviticus 18 emphasizes the reasons for the prohibitions, Leviticus 20 focuses on their penalties. If the penalty for sex with one’s father’s wife was the same whether or not she was one’s mother, there may not have been a need to include a prohibition on one’s mother explicitly.

The text does not mention ego’s grandmother. This may be because Leviticus 18’s expanded list covers four generations beginning with that of ego’s parents—the “father’s house” (בית אב) in which ego was raised.

Guillaume Cardascia, “Égalité et inégalité des sexes en matière d’atteinte aux moeurs dans le Proche-Orient ancien,” Die Welt des Orients 11 (1980): 7–16.

Tikva Frymer-Kensky, “Sex and Sexuality,” The Anchor Bible Dictionary, ed. David Noel Freedman et al. (New York: Doubleday, 1992), 5:1145; Jonathan R. Ziskind, “The Missing Daughter in Leviticus XVIII,” Vetus Testamentum 46 (1996): 125–30.

Ziskind’s argument is a bit more intricate: He suggests that the purpose of the incest prohibitions was actually to elevate women’s status by protecting them from unwanted sexual advances, but that in order for his program to be successful, the author needed to avoid upsetting his readers’ sensibilities. Prohibiting ego’s daughter would seem to undermine the patriarchal order, so including that prohibition would be a bridge too far.

Ziskind, “Missing Daughter,” 129; Jacob Milgrom, Leviticus 17–22 (New York: Doubleday, 2000), 2:1537.

Philo of Alexandria understands the laws this way (Special Laws 3.20).

See Exod 28:42; Lev 20:18.

Translations of LH and Hittite Laws are from, Martha T. Roth, Law Collections from Mesopotamia and Asia Minor, SBL Writings from the Ancient World 6 (Atlanta: SBL, 1995).

See my discussion in “Sexual Prohibitions in the Bible and the ANE: A Comparison,” TheTorah.com (2018).

Susan Rattray, “Marriage Rules, Kinship Terms and Family Structure in the Bible,” in Society of Biblical Literature 1987 Seminar Papers, ed. Kent H. Richards (Atlanta: Scholars Press, 1987), 537–544.

Rattray notes that mother–son incest is “the one case least likely to occur and most universally abhorred.”

In addition to Ibn Ezra, quoted here, this idea appears in modern scholarship. See, for example, Madeline Gay McClenney-Sadler, Recovering the Daughter’s Nakedness: A Formal Analysis of Israelite Kinship Terminology and the Internal Logic of Leviticus 18 (New York: T&T Clark, 2007), 79, 91. (McClenney-Sadler also cites Rattray’s explanation.)

Here ibn Ezra is at odds with the rabbinic interpretation, which assumes the prohibition here only applies to a woman he married. Thus, they split the difference, learning “daughter of one’s wife” from this verse, and “daughter from some other woman” from the verse about granddaughters. See Rashi on both verses.

The Hebrew is from the Ish Shalom text, the English, with many adjustments, is based on William G. Braude and Israel J. Kapstein, trans., Tanna Debe Eliyahu: The Lore of the School of Elijah (Philadelphia: JPS, 1981), 168.

This argument is also made by Don Isaac Abarbanel (ad loc.).

Many scholars have come to this conclusion. See, for example, Elliger, Leviticus, 234; and Baruch Schwartz, The Holiness Legislation, 178.