I. The Scope, Purpose, and Design of the Seventh Commandment
"The seventh commandment is, 'Thou shalt not commit adultery.'" [Thomas Vincent - The Shorter Catechism]
"The design of this commandment is the preservation of chastity amongst men, and the guarding of marriage, or keeping it holy." [Zacharias Ursinus - Commentary on the Heidelberg]
"The purport of this commandment is, that as God loves chastity and purity, we ought to guard against all uncleanness. The substance of the commandment therefore is, that we must not defile ourselves with any impurity or libidinous excess. To this corresponds the affirmative, that we must regulate every part of our conduct chastely and continently." [John Calvin - Institutes]
"This commandment, as we learn from our Lord's exposition of it, given in his sermon on the mount, forbids all impurity in thought, speech, and behaviour." [Charles Hodge - Systematic Theology]
"The seventh commandment requireth the preservation of our own and our neighbour's chastity, in heart, speech, and behaviour." [Thomas Vincent - The Shorter Catechism]
"The sum of this commandment is--the preservations of bodily purity." [Thomas Watson - The Ten Commandments (Modernized)]
II. The Divine Ordinance of Marriage and Conjugal Chastity
"God in this commandment enjoins and sanctions the preservation of chastity and marriage, and hence authorises marriage itself; for whenever God forbids any thing, he at the same time commands and authorises the observance of that which is opposite thereto." [Zacharias Ursinus - Commentary on the Heidelberg]
"The thing implied is that the ordinance of marriage should be observed. 'Let every man have his own wife, and let every woman have her own husband.' 'Marriage is honorable and the bed undefiled.'" [Thomas Watson - The Ten Commandments (Modernized)]
"Marriage is a lawful and indissoluble union between one man and one woman, instituted by God for the propagation of the human race, that we may know him to be chaste, and to hate all lust, and that he will gather to himself out of the whole human race, thus lawfully propagated, an everlasting church, which shall rightly know and worship him; and that it may be a society of labors, toils, cares and prayers, between persons living in a state of matrimony." [Zacharias Ursinus - Commentary on the Heidelberg]
"The strongest proof of the sanctity of the marriage relation in the sight of God, is to be found in the fact that both in the Old and in the New Testaments, it is made the symbol of the relation between God and his people." [Charles Hodge - Systematic Theology]
"Marriage is a type and resemblance of the mystical union between Christ and his church." [Thomas Watson - The Ten Commandments (Modernized)]
"The doctrine which degrades marriage by making it a less holy state, has its foundation in Manicheeism or Gnosticism... The doctrine of the Romish Church on this subject, therefore, is thoroughly anti-Christian." [Charles Hodge - Systematic Theology]
"The special duties belonging to marriage, are love and fidelity. Love is the marriage of the affections. There is, as it were—but one heart in two bodies. Love lines the yoke and makes it easy; it perfumes the marriage relation..." [Thomas Watson - The Ten Commandments (Modernized)]
"Conjugal chastity is to preserve in holy wedlock the order instituted by the wonderful counsel and wisdom of God." "The common and mutual duties of married persons include, 1. Mutual love. 2. Conjugal fidelity, which requires that each one love the other only, and that constantly. 3. A community of good, together with sympathy in each other's sorrows and misfortunes. 4. The training and education of children. 5. Bearing each other's infirmities with a desire to remove them." [Zacharias Ursinus - Commentary on the Heidelberg]
"Moreover, when spouses are made aware that their union is blessed by the Lord, they are thereby reminded that they must not give way to intemperate and unrestrained indulgence. For though honourable wedlock veils the turpitude of incontinence, it does not follow that it ought forthwith to become a stimulus to it." "This excess Ambrose censured gravely, but not undeservedly, when he described the man who shows no modesty or comeliness in conjugal intercourse, as committing adultery with his wife." [John Calvin - Institutes]
III. What Is Forbidden: Adultery, Lust, and Unnatural Defilement
"LXXII. Ques. What is forbidden in the seventh commandment? Ans. The seventh commandment forbiddeth all unchaste thoughts, words, and actions. Q. 1. What is the sin forbidden in the seventh commandment? A. The sin forbidden in the seventh commandment is, all unchastity and uncleanness." [Thomas Vincent - The Shorter Catechism]
"God, now, in this commandment forbids adultery, which is a violation of conjugal fidelity. When God singles out adultery as the most shocking and debasing vice of all the sins which are repugnant to chastity, he at the same time prohibits and condemns all wandering and wanton lusts, whether they be found in married or unmarried persons, and prohibits all other sins and vices contrary to chastity, together with their causes, occasions, effects, antecedents, consequents, &c. And, on the other hand, he enjoins all those virtues which contribute to chastity." [Zacharias Ursinus - Commentary on the Heidelberg]
"The thing expressly forbidden is adultery, to which lust naturally tends, that its filthiness (being of a grosser and more palpable form, in as much as it casts a stain even on the body) may dispose us to abominate every form of lust." [John Calvin - Institutes]
"The fountain of this sin is lust. Since the fall, holy love has degenerated to lust. Lust is the fever of the soul." [Thomas Watson - The Ten Commandments (Modernized)]
"Since both our body and soul are temples of the Holy Ghost, he com mands us to preserve them pure and holy; therefore he forbids all unchaste actions gestures, words, thoughts, desires, and whatever can entice men thereto." [Zacharias Ursinus - Commentary on the Heidelberg]
"As a man may die of an inward bleeding, so he may be damned for the inward boilings of lust, if it is not mortified." [Thomas Watson - The Ten Commandments (Modernized)]
"The acts of unchastity and uncleanness which are forbidden, are either such as are without marriage, or in those that are married. Q. 4. What are the acts of unchastity and uncleanness without marriage forbidden? A. The acts of unchastity and uncleanness without marriage forbidden are-- 1. Self-pollution. 2. Fornication and adultery." "3. Incest... 4. Rape, and all forcing of any into the sin of uncleanness... 5. Sodomy. Q. 5. What are the acts of unchastity and uncleanness forbidden between those that are married, are, all unseasonable and immoderate use of the marriage-bed." [Thomas Vincent - The Shorter Catechism]
"The things which are contrary to marriage are the same as those which conflict with chastity. 1. Fornication and adultery, by which conjugal faith and chastity are violated by one, or both parties. Also incest, unlawful copulation, and abuse of marriage. 2. Hasty and rash divorces... 3. Forbidding to marry." [Zacharias Ursinus - Commentary on the Heidelberg]
IV. The Heinousness, Aggravations, and Spiritual Danger of Adultery
"Q. 7. Wherefore ought all to forbear all unchastity and uncleanness, especially the grosser acts of fornication and adultery? A. All ought to forbear unchastity and uncleanness, especially the grosser acts of fornication and adultery-- 1. Because fornication and adultery is a sin very offensive and dishonourable unto God." [Thomas Vincent - The Shorter Catechism]
"It is a breach of the marriage-oath. When people come together in matrimony, they bind themselves by covenant to each other, in the presence of God, to be true and faithful in the marital relation. Unchastity breaks this solemn oath; and herein adultery is worse than fornication, because it is a breach of the marital bond." "The sin of adultery lies in this: that it is committed with mature DELIBERATION. There is contriving the sin in the mind , then consent in the will , and then the sin is put forth into act . To sin against the light of nature, and to sin deliberately, is like the dye to the wool, it gives sin a tincture, and dyes it of a crimson color." "That which makes adultery so sinful is, that it is NEEDLESS. God has provided a remedy to prevent it. 'To avoid fornication, let every man have his own wife.'"
"Adultery pollutes. The devil is called an unclean spirit. The adulterer is the devil's first-born; he is unclean; he is a moving quagmire; he is all over ulcerated with sin; his eyes sparkle with lust; his mouth foams out filth; his heart burns like mount Etna, in unclean desires. He is so filthy, that if he dies in this sin, all the flames of hell will never purge away his immorality." [Thomas Watson - The Ten Commandments (Modernized)]
"It is a sin against their body, which defileth it, and oftentimes wasteth and consumeth it... (2.) It is a sin against their soul, which doth blind the mind, waste the conscience, and, in the issue, doth bring destruction upon the soul. (3.) It woundeth and blotteth the name." [Thomas Vincent - The Shorter Catechism]
"Wounds of reputation --no physician can heal. When the adulterer dies, his shame lives. When his body rots underground, his name rots above ground. His bastard children are living monuments of his shame." "The adulterer does what lies in him, to destroy the soul of another--and so kills two at once!" "Adultery, without repentance, damns the soul. 'Do you not know that the wicked will not inherit the kingdom of God? Do not be deceived: Neither the sexually immoral nor idolaters nor adulterers nor homosexual offenders . . . will inherit the kingdom of God!'" "The immoral person stands upon the threshold of hell; and when death gives him a push, he tumbles in!" [Thomas Watson - The Ten Commandments (Modernized)]
V. Practical Remedies and Safeguards Against Impurity
"CHASTITY, in general, is a virtue contributing to the purity of body and soul, agreeing with the will of God, and shunning all lusts prohibited by God, all unlawful intercourse and inordinate copulation in connection with all the desires, causes, effects, suspicions, occasions, &c., which may lead thereto, whether in holy wedlock or in a single life." [Zacharias Ursinus - Commentary on the Heidelberg]
"Q. 4. Whereby may we preserve our chastity? A. We may preserve our chastity-- 1. By watchfulness... 2. By diligence in our callings... 3. By temperance in eating and drinking... 4. By abstinence, and keeping under the body... 5. By the fear of God, and awful apprehension of his presence... 6. By faith in Jesus Christ... 7. By application of the promises of cleansing..."
"We must preserve our chastity-- 1. Because we are men and women, and not beasts... 2. Because we are Christians and not heathens... 3. Because we are true believers, our bodies are members of Christ, and temples of the Holy Ghost, and not our own, and therefore ought to be kept clean and holy." [Thomas Vincent - The Shorter Catechism]
"TEMPERANCE is a virtue observing such limits as are becoming to nature, propriety, sound reason and the order of persons, places and times... This is the mother and nurse of all the other virtues, and is the cause of chastity—without which there can be no chastity; for without temperance we cannot be chaste." "MODESTY, or shamefacedness, is a virtue abhorring all uncleanness, joined with shame, grief and sadness, either on account of past impurity, or on account of fear of future uncleanness; having also a desire and purpose to avoid not only uncleanness itself, but everything that might lead to it." [Zacharias Ursinus - Commentary on the Heidelberg]
"Since we are reminded by an express declaration, that it is not in every man's power to live chaste in celibacy although it may be his most strenuous study and aim to do so... do we not oppose God, and nature as constituted by him, if we do not accommodate our mode of life to the measure of our ability? ... The incontinent, therefore, neglecting to cure their infirmity by this means, sin by the very circumstance of disobeying the Apostle's command." "Therefore, while he forbids fornication, he at the same time forbids us to lay snares for our neighbour's chastity by lascivious attire, obscene gestures, and impure conversation." [John Calvin - Institutes]
"Do not come into the company of a whorish woman; avoid her house, as a seaman does a rock. 'Run from her! Don't go near the door of her house!'" "Look to your eyes. Much sin comes in by the eye. 'Having eyes full of adultery.'" "Look to your lips... Look in a special manner to your heart. 'Guard your heart with all diligence.'" "Look to your attire. A wanton dress is a provocation to lust... Where the sign is hung out--people will go in and taste the liquor." "Beware of going to theaters and plays. A play-house is often a preface to a whorehouse." "Take heed of mixed dancing... 'Dancing is not the conduct of a chaste woman—but of the adulteress'" "Labor to get the fear of God into your hearts... Bernard calls holy fear, 'the door-keeper of the soul.'" "To avoid fornication and adultery, let every man have a chaste, entire love to his own wife. He who loves his wife... will not go abroad to drink of muddy, poisoned waters." "Pray against this sin. Luther gave a lady this advice, that when any lust began to rise in her heart, she should go to prayer. Prayer is the best armor against sin; it quenches the wild fire of lust." [Thomas Watson - The Ten Commandments (Modernized)]