Flee from sexual immorality. All other sins a man commits are outside his body, but he who sins sexually sins against his own body. Do you not know that your body is a temple of the Holy Spirit, who is in you, whom you have received from God? You are not your own; you were bought at a price. Therefore honor God with your body.  1 Corinthians 6:18-20

But among you there must not be even a hint of sexual immorality, or of any kind of impurity, or of greed, because these are improper for God's holy people.  Ephesians 5:3

Think you are not guilty cause you haven't cheated?  Bill Clinton didn't think he was guilty because of his "definition" of sex.  Here is the definition of adultery ( one of the top 10!) according to Jesus.

Mathew 5:27-29
 ²⁷"You have heard that it was said, 'Do not commit adultery.  ²⁸But I tell you that anyone who looks at a woman lustfully has already committed adultery with her in his heart. ²⁹If your right eye causes you to sin, gouge it out and throw it away. It is better for you to lose one part of your body than for your whole body to be thrown into hell.

²¹ Submit to God and be at peace with him; in this way prosperity will come to you.
²²Accept instruction from his mouth and lay up his words in your heart.
²³ If you return to the Almighty, you will be restored: If you remove wickedness far from your tent
²⁴ and assign your nuggets to the dust, your gold of Ophir to the rocks in the ravines,
²⁵ then the Almighty will be your gold, the choicest silver for you.
²⁶ Surely then you will find delight in the Almighty and will lift up your face to God.
²⁷ You will pray to him, and he will hear you, and you will fulfill your vows.
²⁸ What you decide on will be done, and light will shine on your ways. Job 22:21-28