Where does the Bible say it is wrong to have sexual fantasies?

Answer:

Just a side note before getting into your question. You asked me a question about whether something is a sin, implying that you don't know of a passage that addresses the issue, but then you proceed to tell me what you believe the answer ought to be. In other words, you are saying that you hold beliefs for which you have no foundation. This isn't how the Bible talks about faith. "So then faith comes by hearing, and hearing by the word of God" (Romans 10:17). Faith and belief are just other words for the idea of trust. Because God said it, I trust God that it is true -- that is faith. Because I have an opinion, I don't always trust it because I've been proven to be wrong so many times. "I believe" isn't a good way to introduce something that you can only express as an opinion. "For do I now persuade men, or God? Or do I seek to please men? For if I still pleased men, I would not be a bondservant of Christ" (Galatians 1:10).

Jesus stated, "You have heard that it was said to those of old, 'You shall not commit adultery.' But I say to you that whoever looks at a woman to lust for her has already committed adultery with her in his heart" (Matthew 5:27-28). The Jews in Jesus' day had come to decide that sin was only in the physical acts. As long as a person didn't commit a sin, then to the Jew it didn't matter what a person thought. Jesus pointed out that sin starts before action is taken. When a person strongly desires (lusts) to do something sinful, he has already committed the sin in his heart. Jesus isn't talking about a passing thought. He is talking about a person who fantasizes and entertains in his mind doing things he knows he should not do.

The reason is that the way you allow yourself to think impacts the direction of your life. "The lamp of the body is the eye. Therefore, when your eye is good, your whole body also is full of light. But when your eye is bad, your body also is full of darkness. Therefore take heed that the light which is in you is not darkness. If then your whole body is full of light, having no part dark, the whole body will be full of light, as when the bright shining of a lamp gives you light" (Luke 11:34-36). The direction you look, the way you think about things, determines how you will act with your body. If you fill your mind with righteous desires, you will tend to behave righteously. Fill your mind with desires for sin, you will tend to commit sins. "For as he thinks in his heart, so is he" (Proverbs 23:7).

"What comes out of a man, that defiles a man. For from within, out of the heart of men, proceed evil thoughts, adulteries, fornications, murders, thefts, covetousness, wickedness, deceit, lewdness, an evil eye, blasphemy, pride, foolishness. All these evil things come from within and defile a man" (Mark 7:20-23).

Society is starting to realize the truth of this. Studies are coming out stating what should have been obvious:

• The more people watch shows depicting sex or hinting at sex, the higher the rate of people actually having sex outside of marriage.
• The more often people see commercials for cigarettes and alcohol, the higher the rate of people smoking and drinking.
• The more time spent playing violent video games, the more violently people tend to behave.
• People who look at pornography are more likely to be sexually active before marriage.

You are what you think.