Exodus 20:14
14 “You shall not commit adultery.
Matthew 5:27-30
Lust
27 “You have heard that it was said, ‘You shall not commit adultery.’ 28 But I say to you that everyone who looks at a woman with lustful intent has already committed adultery with her in his heart. 29 If your right eye causes you to sin, tear it out and throw it away. For it is better that you lose one of your members than that your whole body be thrown into hell. 30 And if your right hand causes you to sin, cut it off and throw it away. For it is better that you lose one of your members than that your whole body go into hell.
1 Corinthians 7:1-9
Principles for Marriage
7:1 Now concerning the matters about which you wrote: “It is good for a man not to have sexual relations with a woman.” 2 But because of the temptation to sexual immorality, each man should have his own wife and each woman her own husband. 3 The husband should give to his wife her conjugal rights, and likewise the wife to her husband. 4 For the wife does not have authority over her own body, but the husband does. Likewise the husband does not have authority over his own body, but the wife does. 5 Do not deprive one another, except perhaps by agreement for a limited time, that you may devote yourselves to prayer; but then come together again, so that Satan may not tempt you because of your lack of self-control.
6 Now as a concession, not a command, I say this. 7 I wish that all were as I myself am. But each has his own gift from God, one of one kind and one of another.
8 To the unmarried and the widows I say that it is good for them to remain single as I am. 9 But if they cannot exercise self-control, they should marry. For it is better to marry than to burn with passion. (ESV)