Matthew 5:28
But I tell you that whoever looks at a woman and cherishes lustful thoughts has already in his heart become guilty with regard to her.
1 Corinthians 6:9-11
Do you not know that unrighteous men will not inherit God's Kingdom? Cherish no delusion here. Neither fornicators, nor idolaters, nor adulterers, nor any who are guilty of unnatural crime,
1 Corinthians 10:20
No, but that which the Gentiles sacrifice, they sacrifice to demons, not to God; and I would not have you have fellowship with one another through the demons.
Galatians 5:19-21
Now you know full well the doings of our lower natures. Fornication, impurity, indecency, idol-worship, sorcery;
Hebrews 13:4
Let marriage be held in honour among all, and let the marriage bed be unpolluted; for fornicators and adulterers God will judge.