How can looking at pornography be adultery, especially since I’m not married?

Answer:

"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).

Typically fornication is a broad word that includes numerous sexual acts where the couple so engaged are not married to each other. This would include adultery, where one or both are married to someone else. See: What is the difference between fornication and adultery? for details.

The topic under consideration was a Jewish tradition not to commit adultery. At first glance, you would suppose that the tradition was nothing more than a quote from one of the Ten Commandments (Exodus 20:14). But Jesus' comments shows us that the Jews had taken this law very literally. They condemned the action of adultery but ignored the things which led up to the act.

Though the Ten Commandments forbade committing adultery, it was understood that adultery was just one example of sexual sins and that all forms of sexual sins were forbidden by this command. Why? Adultery is the violation of the marriage covenant by having sex with someone to whom you are not married. It does not matter if the partner was willing, such as a prostitute, it is still sinful. Notice in Proverbs 6:23-26 that the harlot is also called an adulteress.

"If a man is found lying with a woman married to a husband, then both of them shall die -- the man that lay with the woman, and the woman; so you shall put away the evil from Israel. If a young woman who is a virgin is betrothed to a husband, and a man finds her in the city and lies with her, then you shall bring them both out to the gate of that city, and you shall stone them to death with stones, the young woman because she did not cry out in the city, and the man because he humbled his neighbor's wife; so you shall put away the evil from among you. But if a man finds a betrothed young woman in the countryside, and the man forces her and lies with her, then only the man who lay with her shall die" (Deuteronomy 22:22-25).

This section of Deuteronomy is expanding on what God meant by "You shall not commit adultery." The first example is of a man having sex with a married woman. Both are considered guilty of adultery even though only the woman was married. Both bore the consequence of their sin. The second example is of a man having sex with a woman engaged to be married. Even though she has not yet married, it was considered to be a crime against her future marriage. The man is specifically charged with humbling his neighbor's wife because the intention for marriage is there.

By extension, sex prior to marriage is a violation against a person’s future mate, even though they may not have yet met.

"If any man takes a wife, and goes in to her, and detests her, and charges her with shameful conduct, and brings a bad name on her, and says, 'I took this woman, and when I came to her I found she was not a virgin,' ... But if the thing is true, and evidences of virginity are not found for the young woman, then they shall bring out the young woman to the door of her father's house, and the men of her city shall stone her to death with stones, because she has done a disgraceful thing in Israel, to play the harlot in her father's house. So you shall put away the evil from among you" (Deuteronomy 22:13-14, 20-21).

So while adultery is technically a specific type of sexual sin, it can represent other related sexual sins. There is a technical term for this type of usage; it is called a "metonymy," where one thing stands in for another. We use metonymies all the time. The newspaper may report, "The President of the United States issued a statement saying ...," yet the statement was written by a staff writer and read by a member of the President's staff. Because the statement has the approval of the President, those who wrote and read the statement stand-in for the President. Or even clearer is when the same paper says, "The White House reports ...," when everyone knows houses don't talk. In the same way, the command "You shall not commit adultery" is shown by God to be a metonymy for all sexual sins.

That was a long lead-in to Jesus' statement. The false idea was that only the act of adultery was a sin. Jesus states that the sin starts earlier than the actual coupling. It begins with lust. Jesus called lusting after a woman "adultery in the heart" because the command under consideration was not committing adultery.

Jesus did not say that lust was adultery. He said that lust was adultery in the heart. The two sins have different consequences. Adultery was punishable by death under the Old Law, but lust was not a punishable sin. Adultery could lead to diseases or pregnancy. Lust does not have those consequences. But what Jesus is saying is that the act of adultery and lusting to commit adultery are equally wrong in God's sight.

However, we already showed that adultery can be a representation of other sexual sins. Therefore, fornication and lusting to commit fornication would also be equivalent in regards to sinfulness. And that is what we find elsewhere in the Scriptures:

"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 7:21-23).

Lusting for sin in your thoughts is still sinful, even if you haven't committed the actual sinful act.

Another mistake that you are making is assuming that Matthew 5:28 is the only passage that deals with sexual lust. It is commonly used because it is easy to understand, but it is by no means the only passage.

"Let us walk properly, as in the day, not in revelry and drunkenness, not in lewdness and lust, not in strife and envy. But put on the Lord Jesus Christ, and make no provision for the flesh, to fulfill its lusts" (Romans 13:13-14).

"Lest, when I come again, my God will humble me among you, and I shall mourn for many who have sinned before and have not repented of the uncleanness, fornication, and lewdness which they have practiced" (II Corinthians 12:21).

"Having their understanding darkened, being alienated from the life of God, because of the ignorance that is in them, because of the blindness of their heart; who, being past feeling, have given themselves over to lewdness, to work all uncleanness with greediness" (Ephesians 4:18-19).

"For we have spent enough of our past lifetime in doing the will of the Gentiles -- when we walked in lewdness, lusts, drunkenness, revelries, drinking parties, and abominable idolatries" (I Peter 4:3).

But the strongest passage condemning pornography is: "For this is the will of God, your sanctification: that you should abstain from sexual immorality; that each of you should know how to possess his own vessel in sanctification and honor, not in passion of lust, like the Gentiles who do not know God" (I Thessalonians 4:3-5). The phrase "passion of lust" comes from two Greek words describing things which arouse unlawful sexual desire. Pornography is wrong for the simple reason that God condemns such material. It is not a form of recreation. It is not a personal right. It is a sin.