Deuteronomy 5:18 is one of the Ten Commandments, and it means that sexual faithfulness within marriage is a command from God that protects both the couple and the wider community. The verse forbids sexual relations outside the marriage covenant, which Israel was to treat as a serious offense against God, against a spouse, and against the family line. God spoke this commandment to the whole assembly of Israel at Horeb, as Moses recounted it to a new generation on the edge of the Promised Land.
“You shall not commit adultery.
Deuteronomy 5:18 (WEB)
What Deuteronomy 5:18 Means
The command is short and direct. “You shall not” is a flat prohibition, not a suggestion, and the word “commit” points to a deliberate act rather than a passing temptation. The word “adultery” refers to sexual intercourse with someone who belongs to another person, which in the ancient Israelite setting meant a married woman or a betrothed one. The commandment therefore protects the marriage bond and the clarity of who belongs to whom in a family.
What the verse does not do is list every step toward sin or explain every hard situation a person might face. It names the act that breaks trust and the boundary God draws around marriage. It also does not promise that obedience will remove all pain or that others will always respond fairly. It states what God requires and leaves the reader to trust that the requirement is good.
The Context of Deuteronomy 5:18
Deuteronomy is Moses’ farewell address to Israel before they enter Canaan. Traditionally Moses is named as its speaker, and the book presents itself as a restatement of the law given at Sinai forty years earlier. The original audience is the second generation of Israelites, children of those who left Egypt, now poised to become a settled nation with homes, fields and households of their own.
The verses just before it, Deuteronomy 5:15-17, recall God’s rescue from Egypt, the command to keep the Sabbath, the call to honor parents, and the prohibition of murder. The verses just after it cover stealing, false testimony and coveting. Read in that sequence, adultery sits among commands about a stable, trustworthy community, which explains why the prohibition is framed as protection for the whole people rather than a private rule.
Key Phrases in Deuteronomy 5:18
Matthew 5:27-28
27 “You have heard that it was said, ‘You shall not commit adultery;’ 28 but I tell you that everyone who gazes at a woman to lust after her has committed adultery with her already in his heart.
(WEB)
Jesus takes the commandment deeper, showing that God looks at the heart as well as the outward act. Reading these verses alongside Deuteronomy 5:18 helps you see that faithfulness begins in desire and attention, not only in deeds.
Hebrews 13:4
Let marriage be held in honor among all, and let the bed be undefiled: but God will judge the sexually immoral and adulterers.
(WEB)
This verse affirms that marriage is honorable and that God judges sexual immorality. It gives a New Testament summary of the same concern for faithfulness that the Ten Commandments first set out for Israel.
A Short Prayer From Deuteronomy 5:18
Lord, you know the places in my heart where loyalty is tested and where I have been tempted to wander. Thank you for drawing clear lines that protect the people I love and the trust they place in me. Give me a watchful heart, honest words with those I answer to, and the courage to walk away from anything that pulls me toward betrayal. Help me to honor you in my body, my marriage and my thoughts. Amen.
