Catholic teaching on chastity, adultery, fornication, and the indissolubility of marriage, with the necessary clarifications to ensure that the statements correspond precisely to Sacred Scripture.
1. Adultery
Adultery consists in engaging in sexual relations with someone other than one's own spouse when a valid marriage exists. It is a sin gravely contrary to marital fidelity and to the Sixth Commandment: “You shall not commit adultery” (Exodus 20:14; Deuteronomy 5:18).
Our Lord Jesus Christ confirms the gravity of this sin:
“You have heard that it was said, ‘You shall not commit adultery.’ But I say to you that everyone who looks at a woman with lust has already committed adultery with her in his heart” (Matthew 5:27–28).
Christ condemns not only the external act but also deliberate inward consent to impure desire.
Saint Paul clearly teaches that adultery is incompatible with salvation as long as the sinner voluntarily persists in it:
“Do you not know that the unrighteous will not inherit the Kingdom of God? Do not be deceived: neither the sexually immoral, nor idolaters, nor adulterers, nor the effeminate, nor homosexuals, nor thieves, nor the greedy, nor drunkards, nor revilers, nor swindlers will inherit the Kingdom of God” (1 Corinthians 6:9–10).
And again:
“For be sure of this, that no fornicator or impure person, or covetous person—that is, an idolater—has any inheritance in the Kingdom of Christ and of God” (Ephesians 5:5).
Scripture, therefore, does not present adultery as a minor or merely private failing. It is a grave sin which, if deliberately persisted in without repentance, excludes a person from the Kingdom of God.
2. Fornication
Sacred Scripture frequently uses the term fornication to designate illicit sexual relations outside marriage.
Saint Paul says:
“For this is the will of God, your sanctification: that you abstain from fornication; that each one of you know how to possess his own body in holiness and honor, not in the passion of lust like the Gentiles who do not know God” (1 Thessalonians 4:3–5).
And he adds:
“For God has not called us for impurity, but in holiness” (1 Thessalonians 4:7).
Therefore, sexual relations between people who are not united in a valid marriage contradict the order established by God. Marriage is the proper context for sexual union.
Saint Paul is absolutely explicit:
“Flee from fornication. Every other sin that a man commits is outside the body; but the fornicator sins against his own body. Or do you not know that your body is a temple of the Holy Spirit within you, whom you have received from God, and that you are not your own? You were bought with a price. Therefore glorify God in your body” (1 Corinthians 6:18–20).
For this reason, the unmarried Christian is called to live chastely, abstaining from sexual relations and refusing deliberate consent to impure desires.
3. The Chastity of the Unmarried
Christian chastity does not mean merely refraining physically from sexual relations. It also includes ordering one's thoughts, desires, glances, conversations, and actions according to the will of God.
Our Lord Jesus Christ taught:
“You have heard that it was said, ‘You shall not commit adultery.’ But I say to you that everyone who looks at a woman with lust has already committed adultery with her in his heart” (Matthew 5:27–28).
Saint Paul exhorts us:
“Put to death, therefore, what is earthly in you: fornication, impurity, passion, evil desire, and covetousness, which is idolatry” (Colossians 3:5).
And also:
“But fornication and all impurity or covetousness must not even be mentioned among you, as is fitting among saints. Let there be no filthiness, nor foolish talk, nor crude joking, which are not fitting; but instead let there be thanksgiving” (Ephesians 5:3–4).
The unmarried Christian, therefore, is called to live chastely, keeping both body and soul for God and deliberately avoiding whatever leads to sins against purity.
4. Marriage and Fidelity
Marriage is not merely a romantic relationship. From the beginning, God established a union between man and woman characterized by exclusivity and fidelity.
Genesis states:
“Therefore a man shall leave his father and his mother and cleave to his wife, and they shall become one flesh” (Genesis 2:24).
Our Lord Jesus Christ uses this very text to teach the indissolubility of marriage:
“Have you not read that He who made them from the beginning made them male and female, and said, ‘For this reason a man shall leave his father and his mother and be joined to his wife, and the two shall become one flesh’? So they are no longer two but one flesh. What therefore God has joined together, let no man put asunder” (Matthew 19:4–6).
Marriage, therefore, requires fidelity for as long as both spouses are alive.
5. Divorce and a New Union
The teaching of Jesus Christ is particularly clear:
“Everyone who divorces his wife and marries another commits adultery, and he who marries a woman divorced from her husband commits adultery” (Luke 16:18).
Saint Mark conveys the same teaching:
“Whoever divorces his wife and marries another commits adultery against her; and if she divorces her husband and marries another, she commits adultery” (Mark 10:11–12).
And Saint Paul teaches:
“To the married I give charge, not I but the Lord, that the wife should not separate from her husband (but if she does, let her remain single or else be reconciled to her husband)—and that the husband should not divorce his wife” (1 Corinthians 7:10–11).
Separation between spouses may occur under certain circumstances, but separation does not automatically make someone free to marry another person if that individual remains bound by a valid marriage.
Therefore, as long as one's spouse is alive and the valid marriage bond remains, a new sexual or marital union constitutes adultery.
Saint Paul explains this by means of an analogy involving the marriage bond:
“Thus a married woman is bound by law to her husband as long as he lives; but if her husband dies she is released from the law concerning her husband. Accordingly, she will be called an adulteress if she lives with another man while her husband is alive. But if her husband dies she is free from that law, and if she marries another man she is not an adulteress” (Romans 7:2–3).
6. “Until Death Do Us Part”
Sacred Scripture presents the marriage bond as enduring throughout the spouses' lives.
Saint Paul states:
“A married woman is bound by law to her husband as long as he lives” (Romans 7:2).
And regarding Christian marriage:
“For the wife does not rule over her own body, but the husband does; likewise the husband does not rule over his own body, but the wife does. Do not deprive one another, except perhaps by agreement for a season, that you may devote yourselves to prayer; but then come together again, lest Satan tempt you through lack of self-control” (1 Corinthians 7:4–5).
Marital fidelity, therefore, is a serious obligation before God.
7. Can an Unmarried Person Have Sexual Relations with a Divorced Person?
Here it is necessary to distinguish carefully between different situations.
If a divorced person was truly married and that marriage remains valid because the spouse is still alive, civil divorce does not, by itself, dissolve the marriage bond before God. Sexual relations with that person constitute an illicit union and involve adultery in relation to the existing marriage bond, in addition to constituting fornication on the part of the person who is not married to them.
Christ's teaching is precisely this:
“Everyone who divorces his wife and marries another commits adultery, and he who marries a woman divorced from her husband commits adultery” (Luke 16:18).
However, simply being in the company of, speaking with, or SOCIALIZING with a divorced person is not a sin. Sin occurs when there is consent to or action contrary to chastity: sexual relations, deliberate sexual acts, or, depending on the circumstances, other gravely disordered acts.
8. Civil Marriage and Sacramental Marriage
In any case, Sacred Scripture establishes that the marriage union must be respected and that civil divorce cannot be used as automatic authorization to enter into a new union while a valid marriage remains in force.
Therefore, when a particular case arises, it is necessary to determine canonically whether a valid marriage bond truly exists.
9. Masturbation
Sacred Scripture does not explicitly use the modern word “masturbation,” but it condemns impurity, lust, and sexual acts contrary to the order willed by God.
Saint Paul teaches:
“For this is the will of God, your sanctification: that you abstain from fornication; that each one of you know how to possess his own body in holiness and honor, not in the passion of lust like the Gentiles who do not know God” (1 Thessalonians 4:3–5).
And:
“Flee from fornication” (1 Corinthians 6:18).
Also:
“Those who are in the flesh cannot please God” (Romans 8:8).
Catholic doctrine considers masturbation a GRAVELY DISORDERED act against chastity. In determining subjective moral culpability for mortal sin (the act is objectively grave matter), one must recognize that the matter is always grave, while also considering full knowledge and deliberate consent.
10. Pornography
Pornography is radically contrary to human dignity and the virtue of chastity. Although the Bible does not use the modern term “pornography,” Our Lord condemns even a deliberately lustful gaze:
“Everyone who looks at a woman with lust has already committed adultery with her in his heart” (Matthew 5:28).
Job expresses the need to guard one's eyes:
“I have made a covenant with my eyes; how then could I gaze at a virgin?” (Job 31:1).
And Saint Paul commands:
“But fornication and all impurity or covetousness must not even be mentioned among you, as is fitting among saints” (Ephesians 5:3).
Also:
“Do not be deceived: neither the sexually immoral, nor adulterers, nor the impure will inherit the Kingdom of God” (cf. 1 Corinthians 6:9–10; Ephesians 5:5).
Consequently, deliberately seeking pornographic images or videos, with knowledge of their nature and consent to viewing them, constitutes grave matter against chastity.
11. Impurity Excludes a Person from the Kingdom of God if There Is No Repentance
Saint Paul repeats this teaching with striking clarity:
“Do you not know that the unrighteous will not inherit the Kingdom of God? Do not be deceived: neither the sexually immoral, nor idolaters, nor adulterers, nor the effeminate, nor homosexuals, nor thieves, nor the greedy, nor drunkards, nor revilers, nor swindlers will inherit the Kingdom of God” (1 Corinthians 6:9–10).
And he immediately adds something extremely important:
“And such were some of you. But you were washed, you were sanctified, you were justified in the name of the Lord Jesus Christ and in the Spirit of our God” (1 Corinthians 6:11).
This demonstrates that Christian doctrine does not merely condemn sin: it also offers the path of conversion, forgiveness, and sanctification.
12. The Solution: Live Chastely According to One's State in Life
The Christian response is not to seek exceptions to justify sin, but to live according to the vocation received from God.
Saint Paul says:
“For this is the will of God, your sanctification” (1 Thessalonians 4:3).
And:
“Flee from fornication” (1 Corinthians 6:18).
He also teaches:
“The body is not meant for fornication, but for the Lord, and the Lord for the body” (1 Corinthians 6:13).
A married person must remain faithful to his or her spouse. An unmarried person must practice continence and chastity. A widowed person must also live chastely. A person who is separated must respect the marriage bond as long as it remains in force (the death of a spouse dissolves it). All are called to order their lives according to God.
13. The Interior Struggle Against Impure Thoughts
Chastity also requires resisting bad thoughts to which one deliberately consents.
Saint Paul teaches:
“Whatever is true, whatever is honorable, whatever is just, whatever is pure, whatever is lovely, whatever is gracious, if there is any excellence, if there is anything worthy of praise, think about these things” (Philippians 4:8).
And:
“Put to death, therefore, what is earthly in you: fornication, impurity, passion, evil desire, and covetousness” (Colossians 3:5).
Not every involuntary thought constitutes a sin. Temptation is not sin as long as it is not deliberately accepted. Sin arises when there is voluntary consent to a disordered thought or desire.
14. God Calls Us to Holiness of Body and Soul
The profound reason for Christian chastity is that the human body belongs to God.
Saint Paul declares:
“Do you not know that your body is a temple of the Holy Spirit within you, whom you have received from God, and that you are not your own? You were bought with a price. Therefore glorify God in your body” (1 Corinthians 6:19–20).
For this reason, Christian sexual morality is not simply a set of prohibitions. It is a call to recognize the dignity of the human body, the holiness of marriage, fidelity between spouses, and purity of heart.
15. Summary of Biblical Teaching
Adultery: Sexual relations with someone other than one's own spouse when a valid marriage exists. Scripture expressly condemns it: Exodus 20:14; Leviticus 20:10; Matthew 5:27–28; Matthew 19:4–9; Mark 10:11–12; Luke 16:18; Romans 7:2–3; 1 Corinthians 6:9–10; Hebrews 13:4.
Fornication: Sexual relations outside marriage. Fundamental passages: Acts 15:20; 1 Corinthians 6:18–20; 1 Corinthians 10:8; Galatians 5:19–21; Ephesians 5:3–5; Colossians 3:5–6; 1 Thessalonians 4:3–8; Revelation 21:8.
Divorce and a new union: Matthew 5:31–32; Matthew 19:3–9; Mark 10:2–12; Luke 16:18; Romans 7:2–3; 1 Corinthians 7:10–11.
Chastity: Genesis 39:7–12; Job 31:1; Matthew 5:27–30; 1 Corinthians 6:18–20; 1 Thessalonians 4:3–8; Ephesians 5:3–5; Colossians 3:5–6; Philippians 4:8.
Masturbation and impurity: Although masturbation is not explicitly named in the Bible, its principles concerning bodily holiness, continence, purity, and mastery over the passions are found especially in Matthew 5:27–30; Romans 6:12–13; 1 Corinthians 6:18–20; Galatians 5:16–24; 1 Thessalonians 4:3–8.
Pornography and lustful looking: Matthew 5:27–28; Job 31:1; Psalm 101:3; Philippians 4:8; Ephesians 5:3–5; Colossians 3:5.
Conclusion: Sacred Scripture teaches unequivocally that Christians must practice the virtue of chastity and that adultery and fornication are grave sins. Our Lord Jesus Christ confirms the holiness and permanence of marriage, and Saint Paul warns that those who deliberately persist in fornication, adultery, and impurity will not inherit the Kingdom of God. Yet the same Scripture proclaims that the sinner can be converted: “You were washed, you were sanctified, you were justified in the name of the Lord Jesus Christ” (1 Corinthians 6:11).
Therefore, in the face of sexual sin, the Christian path is repentance, a firm purpose of amendment, confession to a priest, conversion, struggle against temptation, and a chaste life according to one's state in life.
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