sex before marrage
Deuteronomy Chapter 22:20
But if this thing be true, and the tokens of virginity be not found for the damsel:
Deuteronomy Chapter 22:21
Then they shall bring out the damsel to the door of her father's house, and the men of her city shall stone her with stones that she die: because she hath wrought folly in Israel, to play the whore in her father's house: so shalt thou put evil away from among you.
Hebrews Chapter 13:4
Marriage is honourable in all, and the bed undefiled: but whoremongers and adulterers God will judge.