Leviticus 18:18 Meaning: The Law Against a Rival Sister
“‘You shall not take a wife in addition to her sister, to be a rival, to uncover her nakedness, while her sister is still alive.
Neither shalt thou take a wife to her sister, to vex her, to uncover her nakedness, beside the other in her life time.
And thou shalt not take a wife to her sister, to be a rival to her, to uncover her nakedness, besides the other in her life-time.
`And a woman unto another thou dost not take, to be an adversary, to uncover her nakedness beside her, in her life.
And thou shalt not take a wife to her sister, to vex her, to uncover her nakedness beside her, during her life.
Meaning in one sentence
What does Leviticus 18:18 mean? Explore the prohibition of marrying two sisters, the original Hebrew words, and how Christians interpret this law today.
Context
Leviticus 18 sits at the heart of the holiness code, a set of rules God gave Israel to set them apart from the nations around them. The chapter runs through a list of forbidden sexual relationships, mostly between close relatives. Verse 18 comes after warnings against sleeping with a mother, sister, granddaughter, aunt, daughter-in-law, and brother's wife. Then it addresses a specific case: taking a wife's sister as a second wife while the first sister is still alive. The wording echoes the painful story of Jacob, Leah, and Rachel, where two sisters shared a husband and jealousy tore the household apart. This law was meant to spare families that kind of ruin.
Key Words
Three Hebrew words carry the weight of this verse. First, achot (sister) is a word broad enough to cover a full sister, a half-sister, or even a close female relative. It reminds us that the law protects the most intimate family ties. Second, the verb behind 'to be a rival' is tzror, which literally means to pack or bind together, but it carries the force of causing distress, and it appears in the story of Hannah weeping under her rival's taunting (1 Samuel 1:6). This is not a cold legal term; it names the heartache that comes when a household is divided. Third, 'nakedness' (ervah) is the same word used throughout the chapter for shameful exposure. Marrying two sisters, the text says, would drag both women into a shared shame and rivalry that violates God's design for marriage.
How Christians Read This Verse
Christians have read this verse in different ways. Many Protestant commentators, following Jewish interpreters, see it as a straightforward ban against marrying two sisters at the same time, nothing more. They point to the phrase 'while her sister is still alive' and argue the law does not forbid marrying a deceased wife's sister. Others, like John Calvin, read the verse more broadly, suggesting it implies a general disapproval of polygamy. Roman Catholic and Eastern Orthodox traditions, based on later church canons, extend the prohibition to cover marriage with a deceased wife's sister as well, viewing it as an extension of the incest laws in this chapter. Both sides are seeking to honour Scripture, but they arrive at different practical conclusions.
A common misunderstanding
A common misreading is that Leviticus 18:18 explicitly permits a man to marry his wife's sister after the first wife dies, because it only bans taking a sister 'while her sister is still alive.' In fact, most scholars agree the verse only addresses simultaneous marriage of two sisters. It neither permits nor forbids marriage with a deceased wife's sister, that question is simply outside the scope of this text. Other biblical passages and later church teaching address it separately.
Living This Out
This verse calls you to examine the relational cost of your choices. The law was given to protect sisters from being set against each other as rivals. In your own life, the same principle applies: are you making decisions that push family members into competition or cause hidden hurt? Whether it's favouritism, choices that strain a sibling relationship, or a marriage that creates needless friction, God cares about the peace of your household. This week, look for one way to protect a family bond from rivalry. Let love seek the good of the other, not your own advantage.
Main takeaway: God's law protects family bonds from rivalry and shame, calling us to love in ways that do not bring pain to those closest to us.
For Families
For ages 5, 8
God says we should not marry two sisters because it would make them sad and jealous. He wants families to be happy and peaceful.
For ages 9, 12
This verse was given to protect families from the kind of hurt that happened when Jacob married both Leah and Rachel, the two sisters were always fighting. God’s rules aren’t random; they keep us from making choices that tear people apart. Even today, we should think about how our actions affect the people closest to us.
Questions People Ask
Does Leviticus 18:18 forbid all polygamy?
Not directly. The verse specifically forbids marrying two sisters at the same time. Some Christians, including John Calvin, see a broader principle against polygamy here, but the text itself only addresses this one case. Other Old Testament passages show polygamy happening but never commanded. Most Christians today see monogamy as God's original design from Genesis.
Can a man marry his wife's sister after his wife dies?
This verse does not answer that question because it only speaks about taking a sister 'while her sister is still alive.' Many Protestant scholars say the verse leaves that possibility open. Roman Catholic and Eastern Orthodox traditions, however, forbid such marriages based on later church law and a wider reading of the incest prohibitions. Christians disagree on this point.
What does 'to be a rival' mean in the original Hebrew?
The Hebrew word is 'tzror,' which literally means to pack or bind together. In context, it means to cause distress by making a sister a rival wife. The same word is used in 1 Samuel 1:6 where Peninnah 'provoked' Hannah severely. It's not a neutral word, it describes the deliberate harm that comes from setting two women against each other.
Why is this verse in the middle of a list about incest?
The list in Leviticus 18 covers all kinds of prohibited sexual relationships, including close relatives. Marrying two sisters creates a sexual bond between a man and two women who are already blood-related to each other. The law treats it as a violation of the family bond, similar to incest, because it forces sisters into a shared sexual relationship through the same husband.
Is this law still relevant for Christians today?
Most Christians believe the sexual ethics in Leviticus 18 still reflect God's design for marriage, even though we are no longer under the old covenant law. The principle of protecting family relationships and avoiding rivalry in marriage applies directly. The New Testament reaffirms monogamy and calls husbands to love their wives sacrificially, which this law already pointed toward.
For pastors & researchers
Hebrew interlinear, 8 commentaries & word study