What Does It Mean to Commit Adultery in Your Heart? — Matthew 5:27-28

April 10, 2025/BCL/
Photo Credit: ChristianChan / iStock.com

Photo Credit: ChristianChan / iStock.com

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The Seventh Commandment, “‘You shall not commit adultery'” (Ex. 20:14), includes keeping our hearts pure in the area of our sexuality. In the Sermon on the Mount, Jesus teaches,

“You have heard that it was said, ‘You shall not commit adultery.’ But I say to you that everyone who looks at a woman with lustful intent has already committed adultery with her in his heart.” (Matt. 5:27-28)

The Heidelberg Catechism, a highly regarded summary of the Christian faith first published in 1563, has the following to say about the Seventh Commandment:

Q. What is God’s will for us in the seventh commandment?

A. That God condemns all unchastity, and that we should therefore detest it wholeheartedly and live decent and chaste lives, within or outside of the holy state of marriage. (Heidelberg Catechism, Q&A 108)

The Seventh Commandment encompasses more than the physical act of adultery.

God’s command not to commit adultery also includes not committing fornication (sex outside of marriage) and sinful sexual thoughts. The sinful act of lust toward someone is entirely self-focused. It is about self-gratification, viewing the other person as an object to be used for one’s own pleasure. Sexual lusts can enter our minds with little provocation. We need to remain vigilant against lustful desires and not be complacent.

Exercising self-control in the area of sexual purity isn’t just about our will toughing it out; rather, it is built into our life structure, into our community. We pray regularly to our heavenly Father, we avoid tawdry places, we block perverse websites, and we help each other by keeping one another accountable. Keeping our hearts aligned with God’s will for us requires awareness and discipline:

“Watch and pray that you may not enter into temptation. The spirit indeed is willing, but the flesh is weak.” (Matt. 26:41)

We need the help of the Holy Spirit to keep the desire of our hearts pure.

The Christian life is one of sacrificial love for our neighbor, and believers are commanded to fight against lustful desires. By the Spirit we do not complete such desires; rather, we confess them and replace them with a pure desire. The apostle Paul writes about this battle in his letter to the Galatian church,

But I say, walk by the Spirit, and you will not gratify the desires of the flesh. For the desires of the flesh are against the Spirit, and the desires of the Spirit are against the flesh, for these are opposed to each other, to keep you from doing the things you want to do. (Gal. 5:15-16)

When it comes to fighting and controlling sexual desires, thank God we are led by the Spirit and that we are not under law, but under the mercy of Christ. Sexual desire is a gift from God that is to be fulfilled in love within the boundaries of God-ordained marriage of one man to one woman. God has not left his children on their own to fight spiritual battles in the area of sexual temptation. The Holy Spirit dwells in all who trust in Christ alone as their Savior, and God is faithful to help us keep our hearts pure to his glory in all things.

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