And come not near to the unlawful sexual intercourse. Verily, it is a Fahishah [i.e. anything that transgresses its limits (a great sin)], and an evil way (that leads one to Hell unless Allah forgives him). (Al-Isra 17:32)

Wa La Taqrabū Az-Ziná 'Innahu Kana Faĥishatan Wa Sa'a Sabilaan