You Shall Not Commit Adultery: What It Means

The seventh word at Sinai is two words in Hebrew, lo tin’af:

You shall not commit adultery.

Exodus 20:14

It protects marriage, which the Bible treats not as a private arrangement but as a covenant, a binding promise made before God. The prophet Malachi rebuked men who had abandoned their wives by reminding them that “the LORD has been witness between you and the wife of your youth, against whom you have dealt treacherously, though she is your companion, and the wife of your covenant” (Malachi 2:14). Adultery breaks that covenant. It also wounds children, families and whole communities, which is why it sits among the commandments that protect a neighbor, between murder and theft.

The short answer: adultery is sexual unfaithfulness by a married person: sex with someone other than your husband or wife. The commandment protects the faithfulness of marriage, and Jesus extended it from the act to the heart, saying that lustful looking is already adultery “in his heart.” The Bible treats adultery as a serious sin, yet one that can be forgiven, and it gives a hope of restoration to people who have broken it. It is one of the ten words in The Ten Commandments: What Each One Means.

Israel’s law took adultery with deadly seriousness: both the man and the woman involved could be put to death (Leviticus 20:10). Like other ancient law codes, it defined adultery from a man’s point of view, as involving a married woman. Jesus did not keep that imbalance. He applied the same standard to husbands and wives alike (Mark 10:11–12).

The prophets went further and used adultery as the Bible’s main picture for idolatry. When Israel worshiped other gods, they described it as a wife being unfaithful to her husband (Jeremiah 3; Ezekiel 16). Then they used the same picture to show something astonishing about God. The prophet Hosea was told to take back his unfaithful wife:

Go again, love a woman loved by another, and an adulteress, even as the LORD loves the children of Israel, though they turn to other gods.

Hosea 3:1

That is the backdrop for the commandment. Marriage in the Bible is meant to reflect God’s own faithfulness, a love that keeps its promise. Adultery is wrong not only because it breaks a rule, but because it tells a lie about what love is.

The Bible’s best-known adultery is King David’s. From his palace roof he saw Bathsheba, the wife of one of his soldiers, sent for her and slept with her. When she became pregnant, he tried to cover it up, and when that failed he arranged for her husband Uriah to die in battle (2 Samuel 11). One sin led to the next. (What Does ‘You Shall Not Covet’ Mean? traces how it began with a look.)

God sent the prophet Nathan, who told David a story about a rich man who stole a poor man’s only lamb. David was furious at the rich man, and Nathan answered, “You are the man!” (2 Samuel 12:7). David did not make excuses. Psalm 51, by its own heading, is his prayer after Nathan’s visit:

Create in me a clean heart, O God. Renew a right spirit within me.

Psalm 51:10

The story holds two truths together. The damage was real and lasting: a man was dead, a child died, and David’s family was never the same (2 Samuel 12:10–14). And the forgiveness was also real: “The LORD also has put away your sin” (12:13). Both are part of the Bible’s honest picture of this commandment.

In the Sermon on the Mount, Jesus took this commandment where the law could not reach:

You have heard that it was said, ‘You shall not commit adultery;’ but I tell you that everyone who gazes at a woman to lust after her has committed adultery with her already in his heart.

Matthew 5:27–28

He was not saying that attraction is sin, or that a lustful thought is as damaging as an affair. He was saying that unfaithfulness starts long before the bedroom, in what we feed and entertain. That is why most Christian teachers apply his words directly to pornography, which trains the eye to see people as things to use. It is also why many apply them to emotional affairs: sharing with someone else the intimacy, secrets and attention that belong to your spouse.

The Gospel of John also tells of a woman caught in adultery and brought to Jesus to be stoned. He told her accusers, “He who is without sin among you, let him throw the first stone at her,” and when they had all gone, he said to her, “Neither do I condemn you. Go your way. From now on, sin no more” (John 8:7, 11). Many modern Bibles mark this passage, because it is missing from the earliest manuscripts, but churches have long read it as true to Jesus. Both halves matter: no condemnation, and no more sin.

Faithfulness is rarely lost in a single moment. It is usually lost in small steps that seemed harmless. Job described his own guard:

I made a covenant with my eyes; how then should I look lustfully at a young woman?

Job 31:1

A few ways to protect a marriage:

• Invest in your own marriage. Time, attention and affection given to your spouse are the best defense there is.
• Watch the small steps. Private messages, secret meetings and confiding in someone else about your marriage are often how affairs begin.
• Guard your eyes and your screen. Pornography is not a private matter; it shapes how you see your spouse.
• Bring things into the light. A trusted friend, pastor or counselor makes it much harder for temptation to grow in secret.
• If you are single, the commandment still applies: honor other people’s marriages, and the one you may have someday.

If your spouse has been unfaithful to you, their choice is not your fault, and you do not have to carry it alone. Seek help from people you trust. And if you have broken this commandment, hear Paul’s words to a church that included former adulterers: “Such were some of you, but you were washed” (1 Corinthians 6:11).

What is adultery in the Bible?

Adultery is sexual intercourse between a married person and someone who is not their spouse. The commandment in Exodus 20:14 protects marriage as a covenant. Jesus extended it to lust in the heart (Matthew 5:28), and he applied it equally to men and women.

Is an emotional affair adultery?

The Bible does not use the phrase, but many Christian teachers count it as a form of unfaithfulness. Jesus located adultery in the heart, not only in the act, and giving another person the intimacy that belongs to your spouse breaks trust in a similar way, even without sex.

Can adultery be forgiven?

Yes. David committed adultery and was told, “The LORD also has put away your sin” (2 Samuel 12:13). Jesus told the woman brought to him for adultery, “Neither do I condemn you” (John 8:11), and Paul wrote to former adulterers, “you were washed” (1 Corinthians 6:11). God’s forgiveness is offered freely. Trust between spouses may take much longer to rebuild.

Is adultery grounds for divorce in the Bible?

Jesus named sexual immorality as an exception when he spoke against divorce (Matthew 19:9), so most Protestant churches accept adultery as grounds for divorce, though not a requirement. The Catholic Church teaches that a valid sacramental marriage cannot be dissolved, though separation may be allowed. The Orthodox Church permits divorce and remarriage in some cases. Many couples, with help, rebuild their marriages after adultery.

Which commandment is “You shall not commit adultery”?

It is the seventh commandment in Protestant, Orthodox and Jewish counts, and the sixth in Catholic and Lutheran ones. The words are the same in every Bible (Exodus 20:14; Deuteronomy 5:18); Catholic vs Protestant Ten Commandments explains why the numbers differ.