Therefore a man shall leave his father and mother and be joined to his wife, and they shall become one flesh. The instructions God gave in the Bible are for our good. One is that sex should occur exclusively in marriage between a husband and a wife. God is not trying to keep us from happiness, but to protect us from harm and unhappiness. Any form of sexual activity outside the bonds of marriage is wrong, and dangerous.
Human history is filled with examples of the disease, heartache, and misery caused by it.
I have come that they may have life, and that they may have it more abundantly. There is a way which seems right to a man, but its end is the way of death. For I know the thoughts that I think toward you, says the Lord, thoughts of peace and not of evil, to give you a future and a hope. Because narrow is the gate and difficult is the way which leads to life, and there are few who find it. If we confess our sins, He is faithful and just to forgive us our sins and to cleanse us from all unrighteousness.