Thou shalt not Commit Adultery
It is in the Bible, Charlton Heston brought it down from the mountain as part of the Law that would guide and strengthen the newly freed Jewish slaves as they changed and became an independent nation under God. (the Charlton Heston part is a joke!)
Nations throughout history have practiced Polygamy and Fornication. Wickedness was a part of society. The Bible shows this, but never condones it as what God wanted. From the beginning God created husband and wife and made them one. Not husband and wives.
The Bible teaches faithfulness to one mate (understood to be of the opposite sex since procreation was the first order of business). The Bible teaches that we should have a godly seed to glorify God.
Malachi 2:14 Yet ye say, Wherefore? Because the LORD hath been witness between thee and the wife of thy youth, against whom thou hast dealt treacherously: yet is she thy companion, and the wife of thy covenant.
Treacherously, betrayal of trust, deceitfully. Adultery. A grave sin that must be seen for what it is. God instituted marriage and uses it as a symbol of His relationship with the Jewish nation and Christ's relationship with the church. The world should see an example of Christ's love towards us when they look at the marriages of Christians. What they see instead is a divorce rate and incidence of infidelity that rivals the world system.
The book of Malachi is a scathing rebuke to the priesthood of the Jewish nation. They had faltered in their faithfulness toward their families and to their God. We have done the same.
To commit adultery is a sin against your wife/husband, your children, your God, and a shame to the name of God before the world. It is not an 'affair', dalliance, or fling. It is treachery and betrayal of a loved one. Adultery stabs directly into the heart of the offended mate. Many will cast blame upon the other for other deeds that caused the adulterous act. The blame cannot be shifted and the spot cannot be wiped away. It is ugly and we, speaking to the men now, all know that we are capable of such wickedness.(as are the women) Instead of being honest with others and seeking help from temptation, the sinner convinces himself that he can handle it. He then falls into the trap that Satan has set. Reach out for help. If you think you have problems in your marriage before adultery, you will be totally blasted away by the problems that come after the act.
Save your marriage. Be faithful to your spouse in heart, mind and deed.