Overview

The seventh commandment guards the sanctity of marriage and sexual purity. This section (Q70–72) gives the command, what it requires (the preservation of chastity in heart, speech, and behavior), and what it forbids (all unchaste thoughts, words, and actions). As with the sixth, Christ extends its reach to the heart.

The Questions & Answers

Q70. 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)

Q71. What is required in the seventh commandment? A. The seventh commandment requireth the preservation of our own and our neighbour’s chastity, in heart, speech, and behaviour.

Scripture Proofs (ESV):

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

Further proofs: 1 Cor. 7:2–3, 5, 9; Col. 4:6; 1 Pet. 3:2; Eph. 5:11–12.

Q72. What is forbidden in the seventh commandment? A. The seventh commandment forbiddeth all unchaste thoughts, words, and actions.

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, as is proper among saints.” (Eph. 5:3, ESV)

Further proofs: Matt. 15:19; Job 31:1; Prov. 6:25; Col. 3:5; 1 Cor. 6:18.

Exposition: The commandment protects God’s good gift of marriage and the holiness of our bodies. Q71 frames it positively as the preservation of chastity — both our own and our neighbor’s — “in heart, speech, and behaviour,” covering the whole person. Q72’s threefold “thoughts, words, and actions” makes plain, as Christ taught (Matt. 5:28), that purity is not merely external: lust in the heart already breaks the commandment. So it forbids not only the act of adultery but pornography, lustful imagination, coarse and seductive speech, immodesty, and everything that defiles or tempts. Chastity means sexual faithfulness within marriage and abstinence outside it — and purity of heart throughout. The body is “for the Lord” and a temple of the Spirit (1 Cor. 6:13, 19).

Connections

• WLC Q137–139 — the seventh commandment; the duties required (chastity, modesty, marriage, marital love); the sins forbidden (adultery, fornication, all uncleanness in heart, speech, and act).
• 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.

Pastoral & Practical Significance

In an age saturated with sexual images and messages, this commandment speaks with searching relevance. It calls the Christian to a counter-cultural vision: that the body is not our own to use as we please but the Lord’s, a temple of the Holy Spirit, and that sexual faithfulness — chastity in singleness, fidelity in marriage — is part of glorifying God with our bodies (1 Cor. 6:19–20). Christ’s extension of the command to the heart (Q72) 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: flee immorality (1 Cor. 6:18), guard the heart, pursue purity in the power of the Spirit — and know that no sexual sin is beyond the reach of the One who said to the woman caught in adultery, “Neither do I condemn you; go, and from now on sin no more” (John 8:11).

For Memory & Reflection

• Memorize Q71 and Q72; anchor verse: 1 Thessalonians 4:4 (or Matthew 5:28). Note that purity is required “in heart, speech, and behaviour.”
• Christ extends the command to the heart. Where do I tolerate impurity in thought or imagination that I would never act on?
• Q71 calls me to guard my neighbor’s chastity too. How do my words, dress, and conduct help or hinder others’ purity?