“You have heard that it was said, ‘You shall not commit adultery.’ But I say to you that everyone who looks at a woman with lustful intent has already committed adultery with her in his heart.” (Matthew 5:27–28 NIV)
Fornication and adultery are both issues of the heart. It is not what you or I say or think fornication and adultery are that counts in the end, but rather what God says fornication and adultery are and what He thinks about them. Adultery is committed when a married or betrothed person has a sexual encounter with someone who is not his or her spouse. Here in the Gospel of Matthew, Jesus expands adultery to mean not just a physical act but the emotional act occurring in the mind and heart.
Each man should have sexual relations with his own wife, and each woman with her own husband. (1 Corinthians 7:2b NIV)
Sexual relations between a married man and woman are highly encouraged in the Bible just as sexual relations outside of wedlock are strongly discouraged. As a matter of record, the Bible submits many incidents of extramarital sex occurrences, oftentimes not differentiating between whether the sexual encounter was good or evil. Regardless, all extramarital sex is still fornication biblically and is never condoned in the scriptures.
Now concerning the things whereof ye wrote unto me: It is good for a man not to touch [infinitive middle voice—help himself casually to a sexual encounter with] a woman. (1 Corinthians 7:1 KJV)
Exodus 20:14 contains the seventh commandment: “Thou shalt not commit adultery” (KJV). According to Joseph Benson’s Commentary on the Old and New Testaments, “This commandment forbids all acts of uncleanness, with all those desires which produce those acts and war against the soul.” Another comment by the twelfth-century Rabbi Abraham Ben Meir Ibn Ezra states that the word adultery used here signifies the same meaning as harlotry and fornication.
While adultery is a direct assault on the Christian household and a destruction of the bond that unites the family, God’s Word is very specific concerning both premarital and extramarital sex. Technically speaking, fornication is committed when sexual intercourse occurs between unmarried people. Adultery is committed when a married individual has sexual intercourse with someone other than the spouse. One minor distinction is that all adultery is fornication, but not all fornication is adultery. Either way, fornication and adultery are both sin.
Nevertheless, to avoid fornication[s], let every man have [sexually and exclusively] his own wife, and let every woman have [sexually and exclusively] her own husband. (1 Corinthians 7:2 KJV)
God ultimately knows what is good and bad for you physically and spiritually. Rather than letting you guess at things and suffer consequences via trial and error, He has recorded specific information in His holy writ to save you from the heartache and suffering that wrong choices bring. The seventh commandment, bluntly and succinctly recorded in Exodus 20:14 concerning extramarital sex, is an integral part of God’s timeless laws that have never been more relevant than they are today.
You shall not commit adultery. (Exodus 20:14 NIV)