Avoid unlawful sex entirely. Any other sin a person commits is outside the body but those who commit sexual immorality sin against their own body. Do you not know that your body is a temple of the Holy Spirit within you, given by God? You belong no longer to yourselves. (1Corinthians6:18-19)

Do you not know that the wicked will not inherit the Kingdom of God? Make no mistake about it: those who lead immoral lives, or worship idols, or who are adulterers, homosexuals of any kind, or thieves, exploiters, drunkards, gossips or embezzlers will not inherit the kingdom of heaven. (1Corinthians6:9-10)

Anyone who divorces his wife and marries another commits adultery; and whoever marries a woman divorced by her husband also commits adultery. (Luke16:18)

You have heard that it was said: Do not commit adultery. But I tell you this: anyone who looks at a woman to satisfy his lust has in fact already committed adultery with her in his heart. (Matthew5:27-28)

Indeed, it is from the heart that evil desires come - murder, adultery, immorality, theft, lies, slander. (Matthew15:19)