Committing Adultery or Fornication

And do not approach unlawful sexual intercourse. Indeed, it is ever an immorality and is evil as a way.17:32

Meaning:-
immorality: wickedness, immoral behavior, badness, evil, vileness, corruption, dishonesty
Adultery: sex between a married man or woman and someone he or she is not married to
Fornication: sexual intercourse between people not married to each other.