You shall not commit adultery
We must keep our sexual urges in check. Promises are holy to God and when we promises ourselves [in the form of marriage] to another person, He expects us to keep that promise for ever.
We don't have the luxury to grow tired of our mate and then go have sex with other people outside our relationship. We are not allowed to break that promise.
It is good to marry, but it is better not to marry. The chances that we can overstep this Commandment are then much slimmer.
The Adultery Commandment also counts for single people having sex with married people.
The Adultery Commandment also counts for single people having sex with married people.
FINISH
Source: The Bible: Exodus 20
Source: The Bible: Exodus 20