Meaning of Leviticus 18:18

Leviticus 18:18 prohibits a man from taking his wife's sister as a secondary wife and engaging in sexual relations with her during his wife's lifetime. This prohibition is presented within a larger corpus of laws in Leviticus 18 aimed at defining the boundaries of sexual and familial relationships within ancient Israel, distinguishing their practices from those of the surrounding Canaanite cultures. The verse is not about preventing polygamy itself, as other parts of the Old Testament depict it, but rather about a specific and forbidden familial entanglement that would create severe domestic discord and violate the sanctity of both the marital bond and the sisterly relationship. It speaks to the importance of maintaining distinct and respected roles within the extended family and avoiding situations that would inherently foster jealousy, division, and the exploitation of familial ties for sexual gratification.

Context and Background

This verse is part of the Holiness Code (Leviticus 17-26), which outlines laws and regulations intended to guide the Israelites in living a life set apart, reflecting the holiness of God. Leviticus 18 specifically details prohibited sexual relationships, often referred to as "uncovering nakedness," which were common in the surrounding pagan societies but forbidden to Israel. The underlying principle is to maintain social order, familial integrity, and a distinct covenantal identity for the people of God. The prohibition against marrying a wife's sister is distinct from prohibitions against marrying a wife's mother or daughter, indicating a specific concern about the dynamics within the immediate marital family and the potential for exploitation and rivalry.

Key Themes and Messages

• Familial Purity and Integrity: The verse emphasizes the importance of maintaining the sanctity of familial relationships. The bond between a wife and her sister is to be respected, and a man should not introduce a sexual relationship that inherently creates a rivalry and undermines this bond.
• Prevention of Discord: Taking a wife's sister as a co-wife would almost certainly lead to intense jealousy, conflict, and breakdown within the household. The law aims to prevent such domestic turmoil.
• Distinction from Canaanite Practices: The broader context of Leviticus 18 suggests that such practices were likely prevalent and accepted in the religious and social customs of the Canaanites, and Israel was commanded to avoid them.
• Hierarchical Order within Marriage: While not explicitly stated as the sole reason, the prohibition suggests an underlying concern for the primary marital relationship and the avoidance of actions that would demote or dishonor the first wife by introducing her sister into a sexually intimate, competitive position.

Spiritual Significance and Application

Spiritually, this prohibition can be understood as a call to maintain the purity and integrity of our covenantal relationships, particularly our relationship with God and with one another within the body of Christ. Just as the Israelites were called to be set apart, believers are called to live lives that reflect God's holiness. This involves avoiding entanglements that create division, jealousy, or compromise the sacredness of relationships. In a broader sense, it speaks to the importance of honoring boundaries and respecting the distinct roles and bonds that God has established, whether in marriage, family, or the church.

Relation to the Broader Biblical Narrative

While this specific prohibition is unique to the Levitical Law, the underlying principles of familial integrity, avoiding sexual immorality, and living a life set apart resonate throughout the Bible. The New Testament, while not reiterating this exact law, continues to emphasize sexual purity, the sanctity of marriage, and the avoidance of practices that lead to division within the community of faith. Jesus' teachings on divorce and remarriage, for instance, underscore the seriousness with which God views the marital union. The emphasis on love, honor, and mutual respect within families is a consistent theme.

Analogies

One analogy to understand this prohibition is the idea of a professional organization. Imagine a company where a senior executive is forbidden from hiring their spouse's sibling as a direct subordinate in a role that creates an inherent conflict of interest or undue familial pressure on the existing marital relationship. The prohibition is not about preventing the sibling from working at the company, but about avoiding a specific problematic dynamic that could compromise the integrity of both the workplace and the family. Another analogy could be to consider a sports team where a coach is forbidden from actively recruiting and playing their own spouse's sibling in a way that creates obvious favoritism or undermines team cohesion, even if other sibling relationships are permitted.

Relation to Other Verses

• Leviticus 18:6-17: This entire chapter lists prohibited sexual relationships, providing the immediate context for verse 18. These include incestuous relationships and adultery.
• Deuteronomy 27:20, 22: These verses echo the prohibition, specifically cursing the man who lies with his brother's wife and the man who lies with his father's wife. While not directly about the wife's sister, they highlight the concern for prohibited sexual relations within familial structures.
• 1 Corinthians 5:1-13: The Apostle Paul addresses sexual immorality within the Corinthian church, including a case of incest, emphasizing the need for the community to discipline and purify itself from such practices, demonstrating the ongoing importance of sexual purity and maintaining the integrity of the community.
• Hebrews 13:4: "Let marriage be held in honor among all, and let the marriage bed be undefiled, for God will judge the sexually immoral and adulterous." This verse from the New Testament underscores the sanctity of marriage and the prohibition of sexual impurity, aligning with the spirit of Leviticus 18.