Jesus said, “You have heard that it was said, ‘You shall not commit adultery’” (Matthew 5:27) to reveal that God’s standard goes beyond physical actions. He taught that even lustful thoughts are adultery in the heart, showing that true righteousness begins within, not just in outward behavior.
When Jesus spoke these words in the Sermon on the Mount, He wasn’t rewriting the law but deepening its meaning. While the Old Testament condemned physical adultery, Jesus exposed the root issue: lustful desires that begin in the heart. His teaching calls for inner purity, not just external obedience.
This message is just as relevant today, where temptations often start with what you watch, think about, or entertain privately. Jesus’ words challenge you to honor God and others with your thoughts, not just your actions. Keep reading to discover what the Bible actually says and how you can apply it daily for lasting transformation.
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When Jesus delivered the Sermon on the Mount in Matthew 5, He said something that probably shocked His audience:
“You have heard that it was said, ‘You shall not commit adultery.’ But I tell you that anyone who looks at a woman lustfully has already committed adultery with her in his heart.” (Matthew 5:27–28, NIV)
If you pause and think about that, it’s radical. Most people then—and even now—thought adultery was only a physical act. But Jesus dug deeper. He wasn’t just talking about behavior; He was going straight to the heart. Let’s break this down and see why Jesus said it, what the Bible actually teaches, and why it matters for you today.
1. The Context of Jesus’ Words
Jesus was preaching the Sermon on the Mount (Matthew chapters 5–7). In this sermon, He often used the phrase “You have heard that it was said…” followed by “But I tell you…”
This teaching style did two things:
- Revealed the heart of God’s law – The people knew the law of Moses. They knew the Ten Commandments, including “You shall not commit adultery” (Exodus 20:14). But many saw it only as a checklist: don’t sleep with someone who isn’t your spouse.
- Exposed shallow obedience – The Pharisees and teachers of the law focused on external compliance. As long as you didn’t commit the physical act, you were “righteous.” Jesus shattered that thinking.
So when He said, “You have heard it was said…”, He wasn’t changing the law. He was explaining its true meaning.
2. What Adultery Meant in the Old Testament
To understand why this was so shocking, you need to know how the Old Testament treated adultery:
- It was a serious sin – Adultery broke the covenant of marriage, and in the Law of Moses it was punishable by death (Leviticus 20:10).
- It represented unfaithfulness to God – The prophets often used adultery as a metaphor for Israel’s idolatry (Jeremiah 3:8–9, Hosea 1–3). Turning to false gods was like cheating on God.
- It destroyed families and communities – Adultery wasn’t private; it had ripple effects. Betrayal, broken trust, shame, and division always followed.
In short, everyone already knew adultery was wrong. What they didn’t expect was Jesus redefining purity at the heart level.
3. Why Jesus Went Deeper: The Heart of the Issue
Jesus made it clear:
“But I tell you that anyone who looks at a woman lustfully has already committed adultery with her in his heart.” (Matthew 5:28)
Here’s why that matters:
- Sin starts inside – Before an action happens, there’s a thought, a desire, or a fantasy. Jesus cut sin off at the root.
- God cares about motives, not just actions – In 1 Samuel 16:7, God tells Samuel that while humans look at outward appearances, God looks at the heart.
- Lust devalues people – Lust reduces someone to an object for personal gratification, instead of honoring them as God’s creation.
- Adultery of the heart is just as destructive – Even if it never leads to the physical act, it poisons relationships, erodes trust, and distances you from God.
Jesus wasn’t trying to make life harder. He was showing us the true depth of holiness—a righteousness that goes beyond the surface.
4. What This Means for You Today
Let’s be practical. Why does this matter for you in 2025? Because the struggle with lust and purity is still real. In fact, with smartphones, movies, and internet access, it’s probably more intense now than ever.
Here’s what you should take away:
- Adultery isn’t just physical – Jesus said your thought life matters. The battle for purity is often fought in your mind and heart before it ever shows in your actions.
- It’s about honoring God and others – Treating people with dignity means not reducing them to objects of desire.
- Your relationships depend on it – Trust in marriage, dating, or even friendships can be destroyed by unchecked lust.
5. How to Guard Against Adultery of the Heart
Jesus’ teaching isn’t just about condemnation—it’s about transformation. Here are some biblical ways to fight lust and live faithfully:
- Renew Your Mind – Romans 12:2 says, “Do not conform to the pattern of this world, but be transformed by the renewing of your mind.” Fill your mind with God’s Word, not toxic content.
- Guard Your Eyes – Job 31:1 says, “I made a covenant with my eyes not to look lustfully at a young woman.” What you watch, scroll, and linger on shapes your desires.
- Flee from Temptation – 1 Corinthians 6:18 tells us to “flee from sexual immorality.” Don’t flirt with sin; run from it.
- Cultivate Self-Control – The fruit of the Spirit (Galatians 5:22–23) includes self-control. With God’s Spirit, you can resist what once controlled you.
- Focus on Love, Not Lust – True love seeks the best for others. Lust takes. Love gives.
6. The Grace of Jesus in This Command
Here’s the good news: Jesus didn’t just raise the standard and leave us hopeless. He also offered grace and forgiveness.
- For the guilty – Maybe you’ve already failed. You’ve entertained lustful thoughts, watched things you shouldn’t, or even committed adultery. The cross is big enough to cover it. “If we confess our sins, he is faithful and just and will forgive us our sins and purify us from all unrighteousness.” (1 John 1:9)
- For the struggling – Jesus understands temptation (Hebrews 4:15). He gives strength to fight.
- For the broken – Adultery doesn’t have to define your story. Redemption and restoration are possible through Christ.
7. Final Takeaway
So why did Jesus say, “You have heard that it was said, ‘You shall not commit adultery’”? Because He wanted to take you deeper. He wasn’t content with shallow, external obedience. He was after your heart.
Adultery isn’t just about breaking a marriage vow—it’s about faithfulness to God and to people. And it doesn’t start in the bedroom. It starts in the mind and the heart. Jesus calls you to purity not to limit your joy, but to protect it.
FAQs: Why Did Jesus Say “You Have Heard That It Was Said, ‘You Shall Not Commit Adultery'”?
1. Did Jesus change the Old Testament law about adultery?
No. He didn’t change the law but revealed its deeper meaning. He showed that the law wasn’t just about avoiding actions but also about guarding your heart.
2. What’s the difference between lust and love?
Lust takes for self-gratification. Love gives and honors others. Jesus calls you to love, not lust.
3. Is lust really the same as adultery?
In God’s eyes, yes. Jesus said lust in the heart is already adultery because it’s unfaithfulness in desire, even if not in action.
4. Why did Jesus focus on the heart?
Because sin begins inside. Thoughts and desires eventually shape your actions. God values inner purity, not just outward behavior.
5. How serious is lust according to Jesus?
Very serious. In Matthew 5:29–30, Jesus said it’s better to lose your eye or hand than let lust drag you into sin.
6. Does this mean sexual desire is bad?
No. Sexual desire is God-given, but it’s meant for marriage. The problem is when desire is misused outside of God’s design.
7. How can I overcome lust?
By renewing your mind with Scripture, guarding your eyes, fleeing temptation, practicing self-control, and relying on the Holy Spirit.
8. Can someone be forgiven after adultery?
Yes. God offers forgiveness through Christ. King David committed adultery but was forgiven after repentance (Psalm 51).
9. What does this teaching mean for marriage?
It means faithfulness includes thoughts and desires, not just actions. Emotional or mental unfaithfulness matters too.
10. Why does Jesus’ teaching still matter today?
Because the human heart hasn’t changed. Lust, pornography, and infidelity destroy lives. Jesus’ words are timeless guidance for purity and love.
Why did Jesus say, “You have heard that it was said, ‘You shall not commit adultery’”? Discover what the Bible actually teaches about lust, purity, and faithfulness, and why Jesus focused on the heart, not just external actions.
