When a man is involved in porn on the net, does that qualify as fornication? May a woman put her husband away when this happens?
"And I say to you, whoever divorces his wife, except for sexual immorality, and marries another, commits adultery; and whoever marries her who is divorced commits adultery" (Matthew 19:9).
When a person wants to do something, such as divorce their spouse in order to marry someone else, but they can't find scriptural justification for their action, they will either try to dismiss the restriction by saying the command is not relevant today or they will try to broaden the restriction so that what they want is included in the command. In other words, they will either try to subtract from God's word or they will try to add to it.
"Sexual immorality" or "fornication" that appears in the passage above comes from the Greek word porneia. Porneia refers to illicit sexual acts that take place outside of the bonds of marriage, including adultery, homosexual acts, incest, oral sex, and the like.
But the question is whether porneia includes sexual lusts that are not acted upon. The reason this comes up is that Jesus stated, "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 5:28). In this statement, Jesus is not saying that sexual lust is adultery, but that it is equivalent to adultery. In other words, sexual lust for someone who is not your spouse is just as much a sin as actually committing the act of adultery. Still Jesus is not stating that they are the same sin. The major point that Jesus is trying to get us to learn is that desiring to commit a sin and actually committing the sin is not that different to God. The Jews emphasized the physical to the point that they excused or dismissed the spiritual implications of the law. They knew that adultery was wrong, but thought there was nothing wrong with thinking about it -- so long as a person didn't actually do it. Jesus is pointing out that sins originate in the heart (Mark 7:21-23). The only difference between thinking about sin and committing sin is the opportunity to act on your thoughts.
The point is that sexual lust and acts of sexual immorality are equally wrong. Lust is not a lesser sin than adultery as the Jews had been arguing. Jesus did not say that a man looking at woman lustfully was guilty of adultery; he said that he had already been committing adultery in his heart. The only difference between the two sins was the opportunity of action; therefore the two sins are not that much different. The lack of action doesn't make lust less of a sin; yet, lust and adultery are not the same sin.
John makes a similar argument between hatred and murder. "Whoever hates his brother is a murderer, and you know that no murderer has eternal life abiding in him" (I John 3:15). But this does not mean that when you hated your parents for not letting do something that you had murdered them. John's point is that hatred is not a lesser sin than murder. Both are equally wrong. The difference between the two is the opportunity for action. But the lack of action doesn't make the hatred less of a problem; yet, hatred and murder are not the same sin.
In Matthew 19:9, Jesus is referring to the acts of fornication, not just the thoughts of fornication. Several difficulties would arise if thoughts were included, but the most difficult would be proof. "For what man knows the things of a man except the spirit of the man which is in him?" (I Corinthians 2:10). Could a wife demand a divorce because her husband looked at pornography, watched a movie that included scenes of fornication, or looked at a woman walking down the street too long? If a wife was convinced that her husband was thinking about other women, even though she had no evidence of it, could she demand a divorce and then remarry?
Don't get me wrong. Lusting after a woman who is not your wife is sinful. It will keep you out of heaven. It needs to be corrected. However, the porneia in Matthew 19:9 refers to actions of fornication and not the thoughts of fornication. The Greeks had different words for sexual lusts.
If a woman decided to divorce her husband because of his involvement in pornography (and she really should not do so), she would have to remain unmarried for the rest of her life. "Now to the married I command, yet not I but the Lord: A wife is not to depart from her husband. But even if she does depart, let her remain unmarried or be reconciled to her husband. And a husband is not to divorce his wife" (I Corinthians 7:10-11).