From “How to become a Christian”: Chapter 7 – The Ten Commandments – proof that you and I are sinners, not just other people
Are you an adulterer?
You shall not commit adulteryDeuteronomy 5:18 (NIV)
It could be that you have literally committed adultery. Alternatively, you might think that on this one you are in a strong position because you have never physically done this. If so, you need to think again, because Jesus also clarified and broadened this commandment for us:
27You have heard that it was said, ‘Do not commit adultery.’ 28But I tell you that anyone who looks at a woman lustfully has already committed adultery with her in his heart.Matthew 5:27-28 (NIV)
What Jesus meant was that it is not enough simply to avoid literal physical adultery. He said that merely to look upon a woman lustfully is adultery. In other words, even to look upon a woman (or a man) lustfully is regarded by God as being adultery, even if it does not go as far as anything physical. I do not suppose that there is a person anywhere who has never ‘committed adultery in their heart’ by looking lustfully upon a member of the opposite sex.
It is widespread, which is precisely why businesses base so much of their advertising on using sexual imagery. They know very well that every customer is prone to committing adultery in their heart and that this powerful motivation can be used to sell products. I hope that you will accept that you, like me, are guilty of this.
I should add that this also involves fornication (i.e. pre-marital heterosexual sex), pornography and homosexuality. The sin of adultery is a broad one and is not restricted solely to married people. Any sex, or even lustful thought, is sinful unless it is within heterosexual marriage and is with or towards one’s own spouse. God, fully approves of sex within marriage. Remember, it was He who invented sex. Thus we must not get the wrong idea and think that God disapproves of sex. He just reserves it for heterosexual married couples. Our society has largely abandoned that view over the last 40 years, and especially in the last 20 years. But it remains true and it is how God sees it. Consider what apostle Paul says about any misuse of our bodies for sexual sin, whether outside marriage or before marriage:
15Do you not know that your bodies are members of Christ himself? Shall I then take the members of Christ and unite them with a prostitute? Never! 16Do you not know that he who unites himself with a prostitute is one with her in body? For it is said, “The two will become one flesh.” 17But he who unites himself with the Lord is one with him in spirit. 18Flee from sexual immorality. All other sins a man commits are outside his body, but he who sins sexually sins against his own body. 19Do you not know that your body is a temple of the Holy Spirit, who is in you, whom you have received from God? You are not your own; 20you were bought at a price. Therefore honor God with your body.1 Corinthians 6:15-20 (NIV)
Look too at what the writer of the letter to the Hebrews says:
Marriage should be honoured by all, and the marriage bed kept pure, for God will judge the adulterer and all the sexually immoral.Hebrews 13:4 (NIV)
That is how seriously God views it. Our society has grown so used to adultery, fornication, vulgar speech, pornography, sexual promiscuity, and now homosexuality, that it is no longer able or willing to see that there is a problem. But there is. What we do with our bodies and our minds does matter. God will judge us for it. We are not free to do as we wish with our own bodies. That is because they do not actually belong to us. They belong to God, because He made us. Therefore He owns us and is fully entitled to tell us what we can and cannot do.