Does the Torah Prohibit Polygamy? An Examination of Leviticus 18:18

Author: David Wilber

It’s commonly believed that the Bible morally permits polygamy—that is, the practice whereby a man is married to more than one woman at the same time. Whether one believes this practice was a temporary provision in the Old Testament or that the Bible actually endorses this practice, the idea that polygamy was morally acceptable at least at one time in the Bible is seldom questioned.

In this article, I will argue that the Torah actually gives us an explicit prohibition against the practice of polygamy. Note that this article is not intended to address every biblical passage on the basis of which it could be argued that polygamy is permitted. I, along with the rest of the team at 119 Ministries, put together a twenty-page script in which all of those passages are addressed, which will be released in an upcoming video teaching.[1]

This article will focus specifically on a commandment found in Leviticus 18:18, which I think prohibits the practice of polygamy. Here is the commandment:

You shall not marry a woman in addition to her sister as a rival while she is alive, to uncover her nakedness. (Leviticus 18:18)

וְאִשָּׁה אֶל־אֲחֹתָהּ לֹא תִקָּח לִצְרֹר לְגַלֹּות עֶרְוָתָהּ עָלֶיהָ בְּחַיֶּֽיהָ׃

This verse is usually understood as prohibiting only one type of polygamous marriage, specifically a marriage to two sisters while both are alive. The implication of such an interpretation is that a man cannot marry his sister-in-law but polygamy in general is permitted.

However, there are reasons to think that this verse does not necessarily refer to two blood-related sisters but to two women in general. Thus, “sister” would have a broader definition that would include any woman and not just a blood relative. If this interpretation is correct, we therefore have an explicit commandment forbidding polygamy in the Torah. 

Why should we believe that Leviticus 18:18 prohibits all polygamy rather than simply prohibiting a marriage between a man and two literal sisters? Several points can be made to support this conclusion.

First, in Hebrew, “a woman in addition to her sister,” is ishah el-achotah, which literally means “a woman to her sister.” This is an idiomatic expression, which, according to scholar Richard Davidson,[2] is always used in the distributive sense of “one in addition to another.” Consider the following verses in which this exact phrase is used idiomatically:

Five curtains shall be coupled to one another [ishah el-achotah], and the other five curtains shall be coupled to one another [ishah el-achotah]. (Exodus 26:3)

חֲמֵשׁ הַיְרִיעֹת תִּֽהְיֶיןָ חֹֽבְרֹת אִשָּׁה אֶל־אֲחֹתָהּ וְחָמֵשׁ יְרִיעֹת חֹֽבְרֹת אִשָּׁה אֶל־אֲחֹתָֽהּ׃

And you shall make fifty clasps of gold, and couple the curtains one to the other [ishah el-achotah] with the clasps, so that the tabernacle may be a single whole. (Exodus 26:6)

וְעָשִׂיתָ חֲמִשִּׁים קַרְסֵי זָהָב וְחִבַּרְתָּ אֶת־הַיְרִיעֹת אִשָּׁה אֶל־אֲחֹתָהּ בַּקְּרָסִים וְהָיָה הַמִּשְׁכָּן אֶחָֽד׃ פ

Their wings touched one another [ishah el-achotah]. Each one of them went straight forward, without turning as they went. (Ezekiel 1:9

חֹֽבְרֹת אִשָּׁה אֶל־אֲחֹותָהּ כַּנְפֵיהֶם לֹא־יִסַּבּוּ בְלֶכְתָּן אִישׁ אֶל־עֵבֶר פָּנָיו יֵלֵֽכוּ׃

In Exodus 26, you’ll notice that it speaks of the coupling of curtains and clasps “one to the other,” which is literally, “a woman to her sister.” The verse in Ezekiel speaks of the wings of the cherubim touching “one another,” which, again, literally translates to “a woman to her sister.” In Hebrew, this is ishah el-achotah, the exact same phrase used in Leviticus 18:18.

In fact, every time the phrase ishah el-achotah occurs in the Tanakh, it is used in an idiomatic manner, meaning “one to another.”[3] This is also the case with the masculine equivalent of this phrase, ish el-akiw, which literally means, “a man to his brother.” This expression, too, is used idiomatically in the distributive sense of “one in addition to another” in every occurrence.[4]

Thus, when we interpret the phrase ishah el-achotah in light of its consistent usage throughout the Scriptures, Leviticus 18:18 ought to be understood idiomatically and distributively as saying you shall not marry one woman in addition to another woman. Indeed, since this phrase is used in this way everywhere else in the Bible, it doesn’t make sense to interpret Leviticus 18:18 as referring to literal sisters. The word “sister” in Leviticus 18:18, therefore, ought to be understood broadly as a female in general.

Interestingly, this interpretation of Leviticus 18:18 was shared by the Qumran community, a first century Jewish sect from whom we get the Dead Sea Scrolls. For instance, among the Dead Sea Scrolls is what’s known as The Temple Scroll, which contains a commentary on Deuteronomy 17:14-20 concerning kings. According to scholars, this commentary appeals to Leviticus 18:18 as a proof text against the practice of polygamy: 

He may not take a wife from any of the nations. Rather, he must take himself a wife from his father’s house—that is, from his father’s family. He is not to take another wife in addition to her; no, she alone shall be with him as long as she lives. If she dies, then he may take himself another wife from his father’s house, that is, his family.[5]

Scholar and theologian, Angelo Tosato, argues that the interpretation of this verse in the Qumran community best reflects the original meaning of Leviticus 18:18:

Qumran’s interpretation of Leviticus 18:18 is not only correct but even more faithful to the original sense than the interpretation commonly given today.[6]

Second, if the author of Leviticus intended Leviticus 18:18 to be understood as a prohibition against marrying literal sisters, thereby implicitly permitting polygamy in general, it would be very clear grammatically. But the textual evidence suggests something else.

Old Testament scholar and professor, Dr. Gordon P. Hugenberger,[7] explains that, if the intention of Leviticus 18:18 was to prohibit a man from marrying two literal sisters, we would expect the use of the conjunction “and [וְ],” rather than the preposition “to [אֶל],” so that the verse would say “a woman and her sister.” This is the precise grammar of the phrase employed by the author in the preceding verse where he prohibits sexual relations with a woman and her daughter. 

In other words, the fact that the verse uses the preposition “to” rather than the conjunction “and” lends support to my argument that this phrase is intended to be understood idiomatically in the distributive sense. If it were referring to two literal sisters, we would expect the phrasing of the verse to be consistent with the other anti-incest laws of Leviticus 18.

Third, the fact that Leviticus 18:18 prohibits polygamy in general is made all the more clear when we consider the reason for the commandment, which is to prevent rivalry between the two wives: “You shall not marry a woman in addition to her sister as a rival.” This consequence applies to any type of polygamous union, not merely that of a marriage with two literal sisters. As Tosato remarks:

This motivation shows that the act legislated against is deemed criminal, not in itself (and thus it is not a case of an incestuous union; nor more generally of a sexual union retained intrinsically perverse), but is deemed criminal in relation to the man’s first wife who would be damaged. In addition, the harm which the law wants avoided is such (rivalry, enmity) that any woman (and not necessarily a sister of the first wife) is capable of causing.[8]

Indeed, if the reason for this commandment was to avoid rivalry between co-wives, it simply doesn’t make sense that this law should be limited to literal sisters. Throughout history, we’ve seen the contentious relationship between co-wives, whether they were sisters or not. You need to look no further than Abraham’s wives, Sarah and Hagar, to see this. Moreover, the very same language, “as a rival,” used in Leviticus 18:18, is also used in 1 Samuel 1:6 in regard to the contentious relationship between Peninnah and Hannah, the wives of Elkanah (1 Samuel 1:6). And there’s no evidence that these women were literal sisters.

Fourth, the overall literary structure of Leviticus 18 suggests that this is a law prohibiting polygamy in general since it is not part of the same unit of laws as the anti-incest laws. Some people insist that Leviticus 18:18 is dealing with a specific incestuous union involving two literal sisters since it occurs directly after many other laws forbidding various incestuous relations. However, scholars have pointed out that there is a major literary break between verse 17 and 18 in Leviticus 18.

Leviticus 18 presents two separate units of laws—the first unit dealing specifically with laws prohibiting various incestuous relationships and the second unit dealing with laws governing sexual morality more generally. Leviticus 18:18 is part of the second unit and therefore not intended to be included with the anti-incest laws of verses 6-17. 

Theologian Dr. Paul Copan explains:

Each verse in 7-17 begins identically, starting with the noun “the nakedness (of) [erwat],” and it leads up to the command, “You shall not uncover ____’s nakedness.” Also, in each of these verses (except v. 9) an explanation is given for the prohibition (e.g., “she is your mother”); this explanation isn’t found in verse 18, which we would expect if it were an incest prohibition. By contrast, each verse in 18-23 begins with a different construction. Even if you don’t read Hebrew, you can truly just glance at the text and immediately see the difference in structure starting with verse 18. Verses 18-23 each begin with what’s called the waw conjunctive (like our word “and”) followed by a different word than “nakedness” (erwat); also, instead of the consistent use of the negative (lo) plus the verb “uncover” (tegalleh, from the root galah), as in 7-17, here the negative particles are used before verbs other than uncover. Why are these contrasts important? In verses 6-17, we’re dealing with kinship bonds while verses 18-23 address prohibited sexual relations outside of kinship bonds.[9]

All of this leads to the conclusion that Leviticus 18:18 likely refers to any two woman and not merely two literal sisters. Thus, Leviticus 18:18 prohibits a man from marrying another woman in addition to his first wife while she is alive. That is to say, the Torah explicitly prohibits polygamy. This, of course, aligns with God’s original design for marriage as established in Creation. Like homosexuality and adultery in the scope of sexual relationships, polygamy is a deviation from God’s design, and therefore we shouldn’t be surprised to find a commandment in the Torah that prohibits it.

[1] I will link the teaching here once it is released. It addresses why the Torah regulates polygamy, why God "giving" King David Saul's wives is not an endorsement of polygamy, etc., and explains how everything is reconciled in Scripture.

[2] Richard M. Davidson, "Flame of Yahweh: Sexuality in the Old Testament," p. 194

[3] Exodus 26:3, 5, 6, 17; Ezekiel 1:9, 23; 3:13

[4] Genesis 37:19; 42:21, 28; Exodus 16:15; 25:20; 37:9; Numbers 14:4; 2 Kings 7:6; Jeremiah 13:14; 25:26; Ezekiel 24:23; 33:30

[5] 11QT57:15-19, Michael Wise, Marin Abegg and Edward Cook, "Dead Sea Scrolls: A New Translation," p. 485

[6] Angelo Tosato, "The Law of Leviticus 18:18: A Reexamination," CBQ Vol. 46, p. 208

[7] Gordon P. Hugenberger, "Marriage as a Covenant: A Study of Biblical Law and Ethics Governing Marriage, Developed from the Perspective of Malachi," p. 115-116

[8] Tosato, p. 207

[9] Paul Copan, "Is God a Moral Monster: Making Sense of the Old Testament God," p. 113

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About David Wilber

David is first and foremost a passionate follower of Yeshua the Messiah. He is also a writer, speaker, and teacher.

David’s heart is to minister to God’s people by helping them rediscover the validity and blessing of God’s Torah and help prepare them to give an answer to anyone who asks about the hope within them (1 Peter 3:15)…