No Adultery
14 Thou shalt not commit adultery.
Adultery is considered a sexual act with someone other than our spouses.
Remember though, Christ said that to even look at a woman with lust is adultery. So it is not just the physical act.
We must abstain from all lustful temptations and acts which would damage or defile our bodies. This includes images, videos, movies, stories and even relationships which may stir up feelings of lust or passion.
Be careful of your relationships.
Exodus 20:14