A friend of mine admits that the Bible forbids a married person from having sex outside of marriage (i.e. adultery), but he claims it doesn't say anything about unmarried people having sex. Is he right?
No, he is not. The Bible clearly teaches that all sexual relations outside marriage are wrong in God’s eyes. The Bible bluntly says, “Flee from sexual immorality” (1 Corinthians 6:18). This includes any kind of sexual activity apart from marriage.
Remember that God gave us the gift of sex in the first place–and He intended for it to be a source of joy and happiness for us. But He also intended for it to be restricted to marriage. Why? One reason is because it was to be a sign of the unity between a husband and wife. It was, in other words, meant to be an expression of their mutual commitment and love. But sex outside marriage easily becomes selfish, and even boring.
God knows what is best for us, including this important area of our lives. Why ignore His way, when it is best for us in the long run? The Bible warns, “There is a way that seems right to a man, but in the end it leads to death” (Proverbs 14:12) The Bible also promises, “Blessed are they whose ways are blameless” (Psalm 119:1).
Pray for your friend; I can’t help but wonder if he is only looking for an excuse to live a life of self-indulgence and immorality. But there is forgiveness and new life for all who turn to Christ in repentance and faith. Yes, we live in a sex-saturated society–but with God’s help we can follow a far better path.