μοιχεύω

From the study of Matthew 5:28

Range of meaning

To commit adultery. In Greek usage and in Jewish law this meant sexual relations between a man and a woman who was married or betrothed to someone else. When used transitively with the woman as object, it means 'to commit adultery with', 'to seduce', 'to violate' her.

Against the English

'Commit adultery' is accurate. The difference lies in what modern readers mean by adultery: any sexual unfaithfulness by either spouse. The ancient category was narrower and shaped differently.

How it drifted

Modern Western law and custom treat adultery as a symmetrical breach of a marriage by either partner. In Torah (Lev 20:10; Deut 22:22) it was defined by the woman's status. A married man who slept with an unmarried woman was not called an adulterer. A man who slept with another man's wife was, whether or not he himself was married. The wrong was against her husband's marriage and household.

Used elsewhere in the period

Exod 20:14 in the Greek Old Testament: οὐ μοιχεύσεις. Lev 20:10 and Deut 22:22 give the death penalty for both partners. Prov 6:32 says the adulterer 'lacks heart' (sense). In Mark 10:11 Jesus speaks of a man committing adultery 'against her', his own wife, which widens the traditional one-sided definition.

From the study of Matthew 5:27

Range of meaning

To have sex that breaks an existing marriage bond. In Israelite law (Hebrew na'af, Lev 20:10; Deut 22:22–24) and in Greek and Roman law alike, the offence was defined by the woman's status. A man of any status who slept with another man's wife or betrothed committed adultery against that husband. A married man who slept with an unmarried, unbetrothed woman was not called an adulterer under Torah, though his act could be condemned as sexual immorality (porneia) or seduction (Exod 22:16). The word was also used as a picture of covenant betrayal: Israel “committing adultery” with other gods (Jer 3:8–9; Hos 4:13–14; compare Matt 12:39, “an adulterous generation”).

Against the English

English “commit adultery” is accurate at its core: sex that violates a marriage. But modern readers usually hear an offence that is the same for both spouses (“cheating on your husband or wife”) and a private betrayal between two people. The ancient word was lopsided in law and public in effect. It was a crime against a household and a husband's line, punishable by death in Torah (Lev 20:10).

How it drifted

Christian teaching, partly building on Jesus' own sayings (Matt 5:28, 32; 19:9; Mark 10:11, “commits adultery against her”), made men's unfaithfulness count fully as adultery. Modern law and culture later made the concept completely symmetrical and largely private. The English word kept the moral core but lost the legal shape.

Used elsewhere in the period

LXX Exod 20:13 and Deut 5:17 (Greek numbering) have exactly ou moicheuseis. LXX Lev 20:10: whoever “commits adultery with a man's wife”. Sirach 23:22–23 says a wife who bears an heir by another man has “committed adultery”. Philo (On the Decalogue 121–131) calls adultery the greatest of crimes and places it first among the commandments about neighbours. Josephus, Antiquities 3.92, lists it among the Sinai commands. Mishnah Sotah 5:1 says an adulteress becomes forbidden to both her husband and her lover. In the Greco-Roman world, Athenian moicheia law (Lysias 1) and Augustus' Lex Julia de adulteriis (18 BC) likewise defined adultery by the married woman.

From the study of Matthew 5:32

Range of meaning

To commit adultery. In Jewish law and the Old Testament this meant sex between a man and another man's wife or betrothed. It was an offense against that woman's husband. A married man's affair with an unmarried woman was not called adultery. In the passive, said of a woman: 'to be made the object of adultery,' 'to be adulterated.' Moichaomai is the form found in the Septuagint (Jer 3:8; Ezek 16:32), Mark 10:11–12 and Matthew 19:9.

Against the English

KJV, YLT and ESV 'causeth her to commit adultery / makes her commit adultery' treat the passive as active. WEB 'makes her an adulteress' and BSB 'brings adultery upon her' keep more of the passive. NIV 'makes her the victim of adultery' leans furthest toward her being wronged.

How it drifted

Modern 'adultery' means any married person's unfaithfulness, the same for men and women. In the first century it was defined around the wife's marriage bond. That makes it striking that Jesus says the divorcing husband causes adultery and the second husband commits it.

Used elsewhere in the period

Exodus 20:14 and Deuteronomy 5:18 (LXX ou moicheuseis). Leviticus 20:10 defines it as lying with a neighbor's wife. Sirach 23:22–23 describes the wife who leaves her husband and 'commits adultery.' The passive of moicheuō used of a woman occurs in Greek literature and in the Septuagint (e.g. Sirach 23:23 is active, but Jer 3:9 and Ezek 16:32 show the related sense of being defiled).