Deuteronomy 5:18 Meaning: A Commandment for the Heart
“You shall not commit adultery.
Neither shalt thou commit adultery.
Neither shalt thou commit adultery.
`Thou dost not commit adultery.
Neither shalt thou commit adultery.
Meaning in one sentence
Understand the seventh commandment in Deuteronomy 5:18: what it meant for Israel and how Jesus expanded it to include the heart's intentions.
Context
Moses is speaking to a new generation of Israelites, about to enter the Promised Land. He repeats the Ten Commandments, not as new rules but as the foundation of their covenant with God. This command stands among others that protect life, property, truth, and family. It addresses adultery, the breaking of the marriage bond. In a culture where family lineage and covenant faithfulness mattered deeply, this command guarded the heart of community trust. It is not an isolated rule; it belongs to a set that shows how God's people are to treat one another with respect and fidelity.
Key Words
The Hebrew word for adultery here is na'aph (H5003). It almost always means a married man having sex with another man's wife. It is a breach of the marriage covenant, a violation of trust that affects families and the whole community. The command uses an absolute prohibition: lo' (H3808), a clear, strong 'you shall not.' This is not advice; it is a boundary. Interestingly, the same word na'aph is also used in the prophets for Israel's unfaithfulness to God, idolatry as spiritual adultery. So the command points beyond the physical act to the heart's loyalty. Where your devotion goes, your body follows.
How Christians Read This Verse
Jewish tradition has always read this command as forbidding the act of adultery with a married woman. When Jesus taught in Matthew 5:27-28, He expanded the command to include lustful intent. Most Christians see this as the full meaning of the law, not setting aside the command but revealing its depth. The Catholic and Orthodox traditions teach that deliberate lustful thoughts are a violation of this commandment. Many Protestant traditions agree, though some emphasize that the command directly addresses the act, while Jesus applied it to the heart. All hold that the command protects the sacred bond of marriage.
A common misunderstanding
A common mistake is to think this command only forbids the physical act of cheating on your spouse. But Jesus makes clear in Matthew 5:28 that the command also addresses the heart: whoever looks with lust has already committed adultery in their heart. In fact, the Hebrew word na'aph itself often points to a deeper unfaithfulness, used figuratively for abandoning God. The command calls for fidelity not only in body but in every desire and thought.
Living This Out
This week, consider where you give your heart's attention. For the married: are there small compromises that erode trust? A friendship that has crossed a line emotionally? For the single: do you honor the marriages of others by your words and actions? The command is not just a warning; it is an invitation to faithful love. Let it prompt you to thank God for the gift of covenant, and to ask for strength to keep your heart loyal.
Main takeaway: The seventh commandment calls us to faithful love, reflecting God's own covenant faithfulness to His people.
For Families
For ages 5, 8
God says not to break marriage promises. That means we don't try to take someone else's husband or wife. We keep our promises and trust God with our hearts.
For ages 9, 12
Adultery happens when a married person breaks their promise with their spouse by having a special relationship with someone else. God wants us to keep our promises and respect other people's marriages. This command protects families and shows how God is always faithful to us. Jesus even said that looking at someone with lust can break this command in your heart. That's why we ask God to help us keep our thoughts and actions pure.
Questions People Ask
Does this commandment only forbid the physical act of adultery?
The original Hebrew word na'aph refers specifically to sexual intercourse with another man's wife. However, Jesus in Matthew 5:27-28 teaches that the command also addresses the heart: lustful intent is a violation. Christians across traditions see this as the fuller meaning of the law.
What does the Hebrew word for adultery in Deuteronomy 5:18 mean?
The word is na'aph (H5003). It means to commit adultery, usually in the context of a man having sex with a married woman. It is also used figuratively for idolatry in the prophets, showing that adultery is a breach of covenant faithfulness.
Is adultery still considered a sin in the New Testament?
Yes. Jesus affirms the command in Matthew 5:27-28 and expands it to include lust. Paul warns against adultery in 1 Corinthians 6:9-10, listing it among sins that exclude from the kingdom. The New Testament consistently upholds the sanctity of marriage.
Does this commandment apply to unmarried people?
Yes, in two ways. First, it forbids unmarried people from having sex with someone who is married. Second, Jesus' teaching shows that the command calls all people to purity of heart. For the unmarried, it means honoring the marriages of others and living in a way that prepares for faithful love, whether in marriage or singleness.
How does Jesus' teaching in Matthew 5 expand this commandment?
Jesus says that anyone who looks at a woman with lust has already committed adultery in his heart. This shows that the command is not only about outward actions but about inner desires. It calls for a radical purity that begins in the mind and heart.
For pastors & researchers
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