What does it mean to lust in your heart (Matthew 5:28)?

In His Sermon on the Mount, Jesus warns against harboring lust in your heart, regarding it as morally equivalent to committing adultery, even if no physical act occurs. Jesus emphasizes that sin begins in the heart and mind (see Matthew 15:18–20; Mark 7:20–23), not just in outward actions: “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).

Through this teaching, Jesus shows that God’s standard of righteousness is not limited to external behavior, such as obeying the Ten Commandments and Old Testament law (see Exodus 20:14; Deuteronomy 5:18). Righteousness before God comes from a relationship with Jesus Christ, one that encompasses the believer’s whole existence, including inner attitudes and desires. Even our secret innermost sins are not hidden from God. He sees them all (Psalm 90:8; 139:1–4; Luke 8:17; Hebrews 4:13).

Sin prevents people from having a relationship with God and, thus, leads to His judgment. For this reason, Jesus cautions His followers to guard their hearts and take drastic measures to avoid sin: “So if your eye—even your good eye—causes you to lust, gouge it out and throw it away. It is better for you to lose one part of your body than for your whole body to be thrown into hell. And if your hand—even your stronger hand—causes you to sin, cut it off and throw it away. It is better for you to lose one part of your body than for your whole body to be thrown into hell” (Matthew 5:29–30, NLT).

This illustration of gouging out one’s eye or cutting off one’s hand employs hyperbole, a technique that applies exaggeration to make an important point. Jesus is underlining the eternal stakes. Looking with lust in your heart is serious—it leads to hellfire. And it’s better to lose a body part than to have your entire body perish in hell. Followers of Christ must be vigilant in avoiding sin. They must do whatever it takes to remain pure, not just in their actions but in their hearts.

The Greek verb in Matthew 5:28 translated as “lust after” (KJV) or “lustful intent” (ESV) is epithymēsai. It refers to setting one’s heart upon something forbidden. Paul describes lust in your heart as “deceitful desires” (Ephesians 4:22), “harmful desires” (1 Timothy 6:9), and “evil desires” (Romans 6:12). The consequences of not guarding your heart can be fatal. Peter warns that God “is especially hard on those who follow their own twisted sexual desire” (2 Peter 2:10, NLT). These desires wage war against our souls (see James 4:1; 1 Peter 2:11). James describes the dangerous progression of temptation: lusting in the heart drags us into sinful actions and ultimately gives birth to death (see James 1:14–15).

Christ’s warning is universal. Even the one who has not physically acted out in lust has already committed adultery in his or her heart. Lustful thoughts carry the same moral weight as marital infidelity. Jesus calls His followers to pursue purity in both thought and deed. Believers who entertain sinful thoughts and fantasies must recognize their guilt. They must become spiritually accountable to God for their thoughts and intentions.

True righteousness before God requires purity of heart and conduct. Christ’s teaching highlights the need for a transformed heart, which can be achieved only through spiritual renewal and reliance on God. Only because of what Jesus Christ accomplished for us on the cross can we come into right standing with God (2 Corinthians 5:21; Ephesians 2:8–9). When we fall short of the mark with sinful thoughts and actions, we must humble ourselves and acknowledge our offenses to God (see Psalm 32:5).

Thankfully, “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). As we confess and turn from sin, we receive His mercy (Proverbs 28:13). He washes us clean and pure from guilt and sin, creating within us a clean heart wholly devoted to Him (see Psalm 51:1–17). God transforms us by renewing our minds (Romans 12:2).

The most effective defense against lust in your heart is to fill your mind with God-pleasing meditations (Psalm 19:14), setting your thoughts on spiritual, heavenly things (Romans 8:5–6; Philippians 4:8; Colossians 3:2). When you give God the proper place on the throne of your heart and mind, Satan is defeated (James 4:7).