Sexual wrongdoing. Some older Bible translations (like the King James Version) use the word "fornication," while many modern translations use the term "sexual immorality." Both terms are used in the Bible to mean several different things.
What Is Sexual Immorality?
Sexual immorality refers to any type of prohibited sexual intercourse. This means any sexual activity that happens outside of marriage between a husband and wife. For example, in 1 Corinthians 5:1, "sexual immorality" is used to talk about a sin that the church was allowing: a man was living with his stepmother as if she were his wife.
In a list of serious sins in Romans 1:29, Paul includes "depravity," meaning all kinds of wrong sexual acts. In 1 Corinthians, Paul uses "sexual immorality" to mean all kinds of wrong sexual acts (6:13, 18). In 1 Corinthians 7:2, Paul shows there are many different types of sexual sins. He used this as a reason why people in Corinth should marry and have proper sexual relationships with their spouses. One type of sexual sin included in this general meaning is when a married person has sex with someone who is not their spouse.
“Fornication” or "sexual immorality" can also mean the wrong sexual acts between unmarried people. We can see this meaning when the Bible lists it separately from adultery (sex between a married person and someone who is not their spouse). For example, when Jesus listed the sins that come from a person's heart, he included both of these wrong acts (Matthew 15:19; Mark 7:21). Similarly, when Paul listed people who will not enter God's kingdom, he mentioned both groups - the sexually immoral and those who break their marriage promises by having sexual intercourse with others (1 Corinthians 6:9, King James Version).
Adultery
“Sexual immorality” in Matthew 5:32 and 19:9 is usually taken by biblical students today to refer specifically to adultery. The translation of porneia is about understanding rather than just changing words. Experts disagree about whether Jesus’s exception for divorce is about sexual immorality in a general or specific sense. He might have meant only sex outside marriage, or he might have been including it with other sexual sins.
Sexual Immorality as a Symbol
Sexual immorality is often used as a symbol in both the Old Testament and New Testament. Starting with descriptions of Israel and the church as God’s wife or the bride, turning away from God and worshipping false gods are described as adultery (see Jeremiah 2). Ezekiel 16 uses unfaithfulness to marriage as a symbol of Jerusalem’s bad relationship with God. Jerusalem had become an “unfaithful wife” to him.
The first three chapters of Hosea use the relationship of the prophet Hosea and his unfaithful wife, Gomer. Their relationship is used as an example of how Israel had become guilty of adultery against its “husband,” God, by following other gods. In the book of Revelation, the symbolic use of “immorality” and “passionate immorality” is attributed to Babylon the great, the mother of prostitutes (Revelation 14:8; 17:2–4; 18:3; 19:2).