Is it wrong if I think about having sex with someone other than my spouse?

Exodus 20:17“You must not covet your neighbor’s wife, . . . or anything else that belongs to your neighbor.”

Matthew 5:27-28“You have heard the commandment that says, ‘You must not commit adultery.’ But I say, anyone who even looks at a woman with lust has already committed adultery with her in his heart.”

Lust is adultery in the heart. While it is technically true that when we only imagine having sex with someone we have not actually consummated it physically, it is also true that in our heart we have committed adultery. It is clearly destructive to allow our mind and heart to move in this direction.

Matthew 15:19-20“From the heart come evil thoughts, murder, adultery, all sexual immorality, theft, lying, and slander. These are what defile you.”

Mark 7:20-22Then he [Jesus] added, “It is what comes from inside that defiles you. For from within, out of a person’s heart, come evil thoughts, sexual immorality, theft, murder, adultery, greed, wickedness, deceit, lustful desires, envy, slander, pride, and foolishness.”

James 1:14-15Temptation comes from our own desires, which entice us and drag us away. These desires give birth to sinful actions. And when sin is allowed to grow, it gives birth to death.

What we think about doesn’t just come from our mind; it comes from our heart. Our heart is where our desires come from, and those desires become thoughts, which then become actions. Left unchecked, wrong thoughts eventually result in wrong actions. If we continue to think about having sex with someone, our heart will begin to convince our mind that what we want to do is okay.