Mark 7:20-23 ESV / 62 helpful votes

And he said, “What comes out of a person is what defiles him. For from within, out of the heart of man, come evil thoughts, sexual immorality, theft, murder, adultery, coveting, wickedness, deceit, sensuality, envy, slander, pride, foolishness. All these evil things come from within, and they defile a person.”

1 Corinthians 7:2 ESV / 124 helpful votes

But because of the temptation to sexual immorality, each man should have his own wife and each woman her own husband.

Galatians 5:19-21 ESV / 128 helpful votes

Now the works of the flesh are evident: sexual immorality, impurity, sensuality, idolatry, sorcery, enmity, strife, jealousy, fits of anger, rivalries, dissensions, divisions, envy, drunkenness, orgies, and things like these. I warn you, as I warned you before, that those who do such things will not inherit the kingdom of God.

Hebrews 13:4 ESV / 189 helpful votes

Let marriage be held in honor among all, and let the marriage bed be undefiled, for God will judge the sexually immoral and adulterous.