The Bible contrary to popular opinion does not forbid all sexual relations other than within marriage. Fornication for example means nothing more than prostitution. It comes from the word pornia which meant arches where prostitutes plied their trade. This was common in pagan times and often a feature of pagan temple worship. When Paul condemns this practice in the Bible he certainly is not talking about all sexual relations other than marriage. In fact no where in the Bible is consensual sex between two single people who are in a relationship specifically condemned. In modern Bibles the word fornication has been translated into sexual immorality but even under this meaning, most people would certainly not consider consensual sex between two single people in private who are in a relationship sexual immorality. Also there is a list of specific sexual sins clearly stated in Leviticus chapter 18: Leviticus 18 - Passage*Lookup - New International Version - BibleGateway.com
Sex between two consenting single people is not even mentioned in that passage. Yet that passage is supposed to be a comprehensive list of what is sexually forbidden.
With many churches now no longer even considering homosexuality to be a sin even though it actually is clearly specifically condemned in the Bible, it seems silly that a sin that is not clearly defined but is a matter of specualtion based on Bible interpretation ie consensual sex between two single people who are possibly in a long term relationship is still condemned as sin.
Sources:
FORNICATION IN THE SEPTUAGINT
Liberated Christians Polyamory, Swing, Biblical, Sybian Cyber Center
Sexuality | The Family International
Sex between two consenting single people is not even mentioned in that passage. Yet that passage is supposed to be a comprehensive list of what is sexually forbidden.
With many churches now no longer even considering homosexuality to be a sin even though it actually is clearly specifically condemned in the Bible, it seems silly that a sin that is not clearly defined but is a matter of specualtion based on Bible interpretation ie consensual sex between two single people who are possibly in a long term relationship is still condemned as sin.
Sources:
FORNICATION IN THE SEPTUAGINT
Liberated Christians Polyamory, Swing, Biblical, Sybian Cyber Center
Sexuality | The Family International