My friend is considering having sex, and I was wondering where in the Bible it says that sex before marriage is a sin. I know that sex outside of a marriage is a sin, but I can't find where it says before marriage. I would appreciate all of your help!
I appreciate your concern for your friend. It is great to see someone concerned about the physical and spiritual welfare of others.
I could give you a long preacher's lecture about how sex is something that should be saved for the one person you choose to spend your whole life with in marriage, and how people are willing to have sex before marriage themselves but usually don't want "damaged goods" when it comes to finally getting married. However, you asked where in the Bible it says it is a sin. Better always to let the Bible answer your question than man.
There are a number of passages that say to avoid fornication (using the word used in the King James Version of the Bible). That word is a translation of a Greek word that, I am told, includes all sexual activity outside marriage, including before marriage. In some of these verses it is listed along with adultery, which generally refers to one marriage partner having sex with one not his/her spouse (whether that person is married or not). Some of the passages are: Acts 15:29; Colossians 3:5-6; Ephesians 5:3; Galatians 5:19-21 (calling fornication a work of the flesh as opposed to the fruit of the spirit); and 1 Thessalonians 4:3-5.
Ephesians 5:3, for instance, says "But fornication, and all uncleanness, or covetousness, let it not be once named among you, as becometh saints." And 1 Thessalonians 4:3-5 says, "For this is the will of God, even your sanctification, that ye should abstain from fornication: That every one of you should know how to possess his vessel in sanctification and honour; Not in the lust of concupiscence, even as the Gentiles which know not God." Here Paul even equates abstinence with holiness.
In 1 Corinthians 6:9-10, Paul includes fornicators with homosexuals, theives, and drunkards (among others) as people who will not inherit the kingdom of God. "Know ye not that the unrighteous shall not inherit the kingdom of God? Be not deceived: neither fornicators, nor idolaters, nor adulterers, nor effeminate, nor abusers of themselves with mankind, Nor thieves, nor covetous, nor drunkards, nor revilers, nor extortioners, shall inherit the kingdom of God."
Lest one get the impression that sex is all evil, as some preach, the writer of Hebrews says "Marriage is honourable in all, and the bed undefiled: but whoremongers and adulterers God will judge." (Heb 13:4) Marriage makes sex holy and good.
I pray that these scriptures will be of help. I further pray that your friend will pay attention to them.
Thank you for your question.