1 Corinthians 6:18
Flee from sexual immorality. Every other sin a person commits is outside the body, but the sexually immoral person sins against his own body.
1 Corinthians 7:2
But because of the temptation to sexual immorality, each man should have his own wife and each woman her own husband.
1 Thessalonians 4:3-8
For this is the will of God, your sanctification: that you abstain from sexual immorality; that each one of you know how to control his own body in holiness and honor, not in the passion of lust like the Gentiles who do not know God;that no one transgress and wrong his brother in this matter, because the Lord is an avenger in all these things, as we told you beforehand and solemnly warned you. For God has not called us for impurity, but in holiness. Therefore whoever disregards this, disregards not man but God, who gives his Holy Spirit to you.