### Core Meaning & Semantic Range
The Greek verb μοιχεύω (moicheúō), Strong's `{{G3431}}`, directly translates to "to commit adultery." Its etymological root is found in the noun μοιχός (moichos, `{{G3433}}`), meaning "adulterer." The core semantic range of μοιχεύω is thus centered on sexual infidelity within the confines of a marital covenant. It denotes the active transgression of the marriage bond through illicit sexual relations. While its primary meaning is literal, the term also carries significant metaphorical weight in biblical literature, particularly in the Old Testament Septuagint and the New Testament, where it can describe spiritual unfaithfulness or idolatry, likening a people's devotion to other gods or worldly systems to a spouse's unfaithfulness to their partner. This dual application underscores the profound nature of loyalty and covenant in God's economy.
### Biblical Occurrences & Contextual Analysis
In the Septuagint (LXX), μοιχεύω frequently translates the Hebrew verb נָאַף (na'aph, `{{H5003}}`), which likewise means "to commit adultery." Its most prominent Old Testament appearance is in the Decalogue, specifically the seventh commandment: "You shall not commit adultery" ([[Exodus 20:14]], [[Deuteronomy 5:18]]). This establishes adultery as a direct violation of divine law and a severe breach of covenant.
In the New Testament, μοιχεύω appears in crucial contexts:
* **Synoptic Gospels:** Jesus reiterates the seventh commandment, affirming its enduring validity ([[Matthew 19:18]], [[Mark 10:19]], [[Luke 18:20]]). Crucially, in the Sermon on the Mount, Jesus radically expands the understanding of adultery beyond the physical act to include the lust of the heart: "Everyone who looks at a woman with lustful intent has already committed adultery with her in his heart" ([[Matthew 5:28]]). This teaching elevates the standard of righteousness to internal purity, demonstrating that sin originates in the heart. The verb also appears in discussions concerning divorce and remarriage, where Jesus states that remarrying after an unlawful divorce constitutes committing adultery ([[Matthew 5:32]], [[Matthew 19:9]], [[Mark 10:11-12]], [[Luke 16:18]]).
* **Pauline Epistles:** Paul includes μοιχεύω in lists of vices that exclude individuals from the kingdom of God, emphasizing the gravity of the sin ([[1 Corinthians 6:9-10]], [[Galatians 5:19]]). He also cites the commandment in his summary of the law ([[Romans 13:9]]) and uses it to condemn hypocrisy among those who claim to uphold the law but violate it ([[Romans 2:22]]).
* **Epistle of James:** James uses the related noun μοιχαλίδες (moichalides, "adulteresses") in a metaphorical sense, rebuking those who are "friends of the world" as committing spiritual adultery against God: "You adulteresses, do you not know that friendship with the world is enmity with God?" ([[James 4:4]]). This highlights the concept of exclusive devotion to God.
* **Revelation:** While the verb itself does not appear, the concept of spiritual adultery is powerfully conveyed through the imagery of the "great prostitute" and "fornication" (πορνεία, `{{G4205}}`), particularly in relation to the judgment of Babylon ([[Revelation 17:1-5]], [[Revelation 18:3]]).
### Related Words & Concepts
The study of μοιχεύω is enriched by examining its relationship with other biblical terms:
* **μοιχαλίς (moichalis, `{{G3430}}`)**: "adulteress."
* **μοιχαλικός (moichalikos, `{{G3429}}`)**: "adulterous."
* **μοιχεία (moicheia, `{{G3432}}`)**: "adultery" (the act or state).
* **μοιχός (moichos, `{{G3433}}`)**: "adulterer."
* **πορνεύω (porneuō, `{{G4203}}`)**: "to commit fornication," "to prostitute oneself." While μοιχεύω is specifically about marital infidelity, πορνεύω is a broader term for all illicit sexual activity, often including adultery. However, in some contexts, πορνεία (porneia, `{{G4205}}`) can encompass μοιχεία.
* **Hebrew Equivalents:** In the LXX, μοιχεύω primarily translates נָאַף (na'aph, `{{H5003}}`). Another related Hebrew term is זָנָה (zanah, `{{H2181}}`), "to commit fornication," which is frequently used metaphorically for Israel's idolatry or spiritual unfaithfulness to God, a concept paralleling the metaphorical use of adultery.
The concept of "covenant" is intimately linked, as adultery is a breach of the marital covenant, which itself is often presented as a microcosm of God's covenant with His people. Purity, fidelity, and the sanctity of marriage are all interwoven concepts.
### Theological Significance
The theological significance of μοιχεύω is profound and multi-layered:
1. **Violation of Divine Law:** Adultery is explicitly forbidden by God's Ten Commandments, marking it as a direct transgression against His holy character and His established order for human relationships. It represents a fundamental disrespect for God's authority and His design for marriage.
2. **Sanctity of Marriage:** The prohibition of adultery underscores the sacredness and indissolubility of the marriage bond, which God instituted as a unique, exclusive, and lifelong union. Marriage is presented as a covenant reflecting Christ's relationship with the Church ([[Ephesians 5:22-33]]), making adultery a desecration of a divine institution.
3. **Holiness and Purity:** Jesus' teaching in [[Matthew 5:28]] elevates the understanding of adultery from a mere external act to a matter of the heart. This emphasizes that God's demand for holiness extends to one's inner thoughts and desires, revealing the pervasive nature of sin and the need for internal transformation.
4. **Spiritual Adultery/Idolatry:** The metaphorical use of adultery to describe unfaithfulness to God (e.g., [[James 4:4]]) highlights God's expectation of exclusive devotion from His people. Idolatry, or placing anything above God, is seen as a spiritual betrayal, akin to a spouse's infidelity. This metaphor reinforces God's jealousy for His people's affections and His covenant faithfulness.
5. **Consequences and Judgment:** The New Testament consistently lists adultery among sins that prevent entry into the kingdom of God without repentance ([[1 Corinthians 6:9-10]], [[Galatians 5:19]]). It brings spiritual defilement, societal breakdown, and divine judgment.
6. **Call to Repentance and Forgiveness:** While condemning the sin, the New Testament also presents God's grace and forgiveness for those who repent. The narrative of the woman caught in adultery (though textually debated, [[John 8:1-11]]) powerfully illustrates Jesus' compassion and call to "go, and from now on sin no more."
### Summary
The Greek verb μοιχεύω (moicheúō, `{{G3431}}`) fundamentally means "to commit adultery," signifying the act of sexual infidelity within marriage. Its usage across the Old Testament Septuagint and the New Testament reveals its gravity as a direct violation of God's law, most notably the seventh commandment. Jesus' teachings profoundly expanded its meaning to include the lustful intent of the heart, emphasizing the internal dimension of sin. Beyond its literal sense, μοιχεύω and related terms are powerfully employed metaphorically to describe spiritual unfaithfulness and idolatry, portraying humanity's turning away from God as a betrayal akin to marital infidelity. Theologically, the study of μοιχεύω underscores the sanctity of the marital covenant, God's demand for exclusive devotion and internal purity, and the serious consequences of sin, while simultaneously pointing to the availability of divine grace and forgiveness through repentance.
TRV