Overview

The seventh commandment guards the sanctity of marriage and sexual purity. This section gives the commandment (Q137), the duties it requires — the preservation of chastity in body, mind, affections, words, and behavior (Q138), and the sins it forbids — all uncleanness and whatever leads to it (Q139). The Larger Catechism’s treatment is searching and comprehensive, reaching the heart and its inclinations.

The Questions & Answers

Q137. Which is the seventh commandment? A. The seventh commandment is, Thou shalt not commit adultery.

Scripture Proofs (ESV):

“You shall not commit adultery.” (Exod. 20:14, ESV)

Q138. What are the duties required in the seventh commandment? A. The duties required in the seventh commandment are, chastity in body, mind, affections, words, and behaviour; and the preservation of it in ourselves and others; watchfulness over the eyes and all the senses; temperance, keeping of chaste company, modesty in apparel; marriage by those that have not the gift of continency, conjugal love, and cohabitation; diligent labour in our callings; shunning all occasions of uncleanness, and resisting temptations thereunto.

Scripture Proofs (ESV):

“…that each one of you know how to control his own body in holiness and honor.” (1 Thess. 4:3–5, ESV)

“I have made a covenant with my eyes; how then could I gaze at a virgin?” (Job 31:1, ESV)

Further proofs: 1 Cor. 7:2, 9, 36; Prov. 5:18–20; 1 Tim. 2:9; Col. 4:6; 2:23.

Q139 — the sins forbidden (summarized): The sins forbidden in the seventh commandment, besides the neglect of the duties required, are, adultery, fornication, rape, incest, and all unnatural lusts; all unclean imaginations, thoughts, purposes, and affections; all corrupt or filthy communications, or listening thereunto; wanton looks, impudent or light behaviour, immodest apparel; the prohibiting of lawful, and dispensing with unlawful marriages; the keeping of places conducing to uncleanness; idleness, gluttony, drunkenness, unchaste company; lascivious songs, books, pictures, dancings, stage plays; and all other provocations to, or acts of uncleanness, either in ourselves or others.

Scripture Proofs (ESV):

“But I say to you that everyone who looks at a woman with lustful intent has already committed adultery with her in his heart.” (Matt. 5:28, ESV)

“But sexual immorality and all impurity or covetousness must not even be named among you.” (Eph. 5:3–4, ESV)

Further proofs: Matt. 15:19; Prov. 7:5, 21–22; Gen. 39:7–10; Rom. 13:13; Gal. 5:19; 1 Pet. 4:3.

Exposition: The commandment protects God’s good gift of marriage and the holiness of the body. The Larger Catechism’s distinctive thoroughness appears in both directions. Positively (Q138), it requires not merely abstaining from adultery but cultivating chastity “in body, mind, affections, words, and behaviour” — including “watchfulness over the eyes and all the senses,” “modesty in apparel,” “temperance,” “diligent labour in our callings” (idleness breeds lust), and the shunning of all occasions of uncleanness. Negatively (Q139), it reaches far beyond the act to “unclean imaginations, thoughts, purposes, and affections,” “corrupt or filthy communications,” “wanton looks,” immodest dress, and the whole industry of provocations — “lascivious songs, books, pictures, dancings, stage plays.” As Christ taught, the commandment judges the heart’s lust (Matt. 5:28), and so it calls for vigilance over the inner life and the deliberate avoidance of temptation’s occasions.

Connections

• WSC Q70–72 — the seventh commandment, its duties and sins.
• WCF 24 (Of Marriage and Divorce) — marriage as the honorable estate this commandment protects.
• Loci: The seventh commandment; chastity and purity; marriage; the body as the Spirit’s temple (1 Cor. 6:19–20).

Pastoral & Practical Significance

In an age saturated with sexual images and messages, this commandment speaks with searching relevance — and the Larger Catechism’s wisdom is intensely practical. It does not merely say “do not commit adultery”; it gives a whole strategy for purity. Positively, it calls us to guard the eyes and senses, to dress and speak modestly, to keep chaste company, to work diligently (since idleness invites temptation), and — crucially — to shun the occasions of sin rather than flirt with them, as Joseph fled Potiphar’s wife (Gen. 39). Negatively, it names the provocations honestly, including the entertainments and media that inflame lust, which in our day multiplies the relevance many times over. Christ’s extension of the command to the heart (Q139) leaves no one self-righteous: the secret lust, the wandering eye, the private indulgence all fall under it — so this commandment humbles us and drives us to grace. And grace is exactly what the gospel offers here: Christ pursued an unfaithful people with a faithful love (Eph. 5:25–32), and His cleansing covers every sexual sin for the repentant. For those battling lust, pornography, or shame, the message is both holiness and hope: pursue purity in the Spirit’s power, flee the occasions of sin, and know that no sexual sin is beyond the reach of the One who said, “Neither do I condemn you; go, and from now on sin no more” (John 8:11).

For Memory & Reflection

• Memorize Q137 and the heart of Q138; anchor verses: 1 Thessalonians 4:3–5 and Matthew 5:28.
• Q138 calls me to shun the occasions of sin. What “occasions” — media, company, habits — am I tolerating that I should flee?
• Purity is required “in body, mind, affections, words, and behaviour.” Where do I guard the outward act but tolerate the inward lust?