Exodus 20:14 “You shall not commit adultery.”
“After securing the life, the Lord proceeds to secure that part of property which is often as dear, or dearer to human creatures, than life itself.” (Thomas Coke) “Marriage, according to the original institution, made the husband and wife ‘one flesh’ (Genesis 2:24); and to break in upon this sacramental union was at once a crime and a profanity. Adulteresses and their paramours were in most ancient nations liable to be punished with death by the injured party; but the adultery of a married man with an unmarried woman was thought lightly of. The precept of the Decalogue binds both man and woman equally.” (The Pulpit Commentaries) “Adultery destroys marriage and the home, the foundations of society (cf. Matth 5:27-28; 1 Cor 6:9-20).” (Dr. Thomas Constable)
Jesus reveals the intended standard; He desires your purity of heart soul and mind. Jesus said: “You have heard that it was said to those of old, 'You shall not commit adultery.' But I say to you that whoever looks at a woman to lust for her has already committed adultery with her in his heart.” (Matthew 5:27-28) “Wild and evil theories may be abroad, new schemes of social order may be recklessly invented and discussed; yet, when the institution of the permanent family is assailed, every thoughtful man knows full well that all our interests are at stake in its defence, and the nation could no more survive its overthrow than the Church.” (Expositor's Bible Commentary)