Adultery

What adultery is

In the Old Testament, adultery is sexual union between a married person and someone other than their spouse (Exodus 20:14; Leviticus 20:10). It ranks among the Ten Commandments because marriage is not just an arrangement. It is a covenant, a binding promise made before God.

Malachi 2:14 calls a wife “your companion and your wife by covenant,” with the Lord as witness. Adultery is first of all covenant-breaking: it betrays a sworn promise.

What it represents physically

Genesis 2:24 says husband and wife become “one flesh.” Sex is meant to enact and renew that union: a whole-life giving of yourself, sealed bodily.

Paul builds on this in 1 Corinthians 6:15–20. Joining your body to someone outside the covenant creates a “one flesh” bond that contradicts the real one. He calls sexual sin uniquely a sin “against his own body,” because your body belongs to the Lord and is a temple of the Spirit.

Adultery says with the body something the heart and covenant deny. That is why it wounds so deeply: it tears apart something God joined.

What it represents spiritually

The prophets repeatedly describe idolatry as adultery. Israel is God’s bride, and turning to other gods is unfaithfulness:

• Hosea marries an unfaithful wife as a living parable of God’s love for faithless Israel, and of His pursuit of her anyway.
• Jeremiah 3 and Ezekiel 16 describe Israel as a wife who gave herself to lovers.
• James 4:4 calls believers who love the world “adulteresses.”

Ephesians 5:25–32 then reveals that human marriage was always meant to picture Christ and the church. A husband’s faithfulness reflects Christ’s faithfulness.

So adultery is more than a private sin against a spouse. It misrepresents God’s faithful love. And every idolatry, giving our heart’s ultimate devotion to something other than God, is a kind of spiritual adultery. The two are mirrors: how we keep covenant with our spouse reflects how we keep covenant with God.

Looking with lust: what Jesus meant

In Matthew 5:27–28 Jesus says whoever looks at a woman “to lust after her” has already committed adultery in his heart.

The Greek implies purpose. The phrase is roughly “looks in order to desire her.” The verb (epithymeō) is the same one the Greek Old Testament uses in the tenth commandment: “You shall not covet your neighbor’s wife.” Jesus ties the seventh commandment to the tenth. Lust is mentally taking what isn’t yours.

Noticing is not lusting. Seeing that a woman is attractive, or feeling a sudden pull, is temptation, not sin. Jesus “was tempted in every way that we are, yet was without sin” (Hebrews 4:15). The sin is the second look: lingering, fantasizing, welcoming the desire.

You can’t stop birds flying over your head, but you can stop them building a nest in your hair. (saying often attributed to Luther)

“Equivalent” in what sense? The root is the same: the heart has already been unfaithful, so no one is righteous just because he never acted. The consequences are not identical. Physical adultery also betrays and wounds a spouse, a family and another person. Jesus is levelling our pride, not saying the act and the thought do equal damage.

Fighting it by the letter: cutting off the hand

Jesus continues: if your right eye or hand causes you to sin, cut it off (Matthew 5:29–30). The church has almost universally read this as hyperbole. Origen is reported to have taken a similar text literally by castrating himself, and the church rejected that reading. The eye is not the source: adultery comes “out of the heart” (Matthew 15:19). A one-eyed man can still lust.

The hyperbole’s point is real: be radical about removing occasions of sin, even when it costs you something you value. In practice:

• Make a covenant with your eyes (Job 31:1). Decide in advance where your eyes won’t go, and look away immediately rather than negotiating.
• Flee, don’t reason. Joseph ran from Potiphar’s wife (Genesis 39); Paul says “flee from youthful passions” (2 Timothy 2:22).
• Make no provision for the flesh (Romans 13:14). Filters and accountability software, deleting certain apps or accounts, no phone alone late at night, changed routes or habits, declining situations with a specific person.
• Bring it into the light. Tell a trusted brother, a pastor, or your wife where appropriate. Secrecy feeds lust; confession weakens it (James 5:16).
• Pray in the moment. “Turn my eyes away from worthless things” (Psalm 119:37).

Fighting it by the spirit: seeing what it really is

Rules alone tend to fail, because suppressed desire pushes back. The deeper work is seeing lust truly until it loses its appeal.

Lust turns a person into an object. The woman you’re looking at bears God’s image. She is someone’s daughter, maybe someone’s wife, with a soul and a story. Paul tells Timothy to treat younger women “as sisters, with absolute purity” (1 Timothy 5:2). Practise that reframing in the moment: she’s a sister, not a commodity.

Lust is a counterfeit of covenant love. Real intimacy gives the whole self, permanently, to one person. Lust wants the pleasure without the giving, the commitment or the person. Seen that way it is a cheap, thin imitation, not a richer version of love.

It is a symptom of a hungry heart. Lust often flares when we’re stressed, lonely, bored, rejected or feeling insignificant. Ask what you’re really hungry for, often comfort, escape or feeling wanted, and take that need to God and to legitimate places.

Replace, don’t just remove. Thomas Chalmers called it “the expulsive power of a new affection”: a heart is freed from a lesser love by a greater one. Delight in God (Psalm 16:11; 37:4), and turn your desire toward your wife. Proverbs 5:18–19 commands it: “rejoice in the wife of your youth.” Investing in your marriage is part of the fight.

Walk by the Spirit. “Walk by the Spirit, and you will not gratify the desires of the flesh” (Galatians 5:16). Change is ultimately God’s work renewing the mind (Romans 12:2), fed by Scripture, prayer, worship and fellowship, not willpower alone.

When you fail

Jesus’s teaching was meant to show that everyone needs grace, not to crush people. David committed actual adultery and was restored (Psalm 51). Jesus told the woman caught in adultery, “Neither do I condemn you… Now go and sin no more” (John 8:11). Forgiveness comes first, then the call to change.

“If we confess our sins, He is faithful and just to forgive us.” (1 John 1:9)

Shame drives people back into hiding and back into the sin. Grace gives the security to keep fighting.