The Holy Prophet [s] said: "It is written in the Turah: 'I am Allah, the killer of murderers and distractor of fornicators."
Al-Kafi, vol. 5, p. 554
Imam Sadiq [a] said: "There are six effects for a fornicator, three of which are in this world and the other three will be in the next world. Those that occur in this world are: taking the honour of the person and defaming the one; causing the one to become poor; and shortening the length of life, (i.e. hastening one's death). Then, those which will be in the Hereafter are: the wrath of Allah, graveness in Reckoning, and residing in Fire eternally."
Al-Kafi, vol. 5, p. 541
The Holy Prophet [s] said again from the Turah:
"O' people, do not commit fornication because your wives will do the same, too. That which you sow, you will reap." (The same as you do will be done to you).
Al-Kafi, vol.5, p.554
The Holy Prophet [s] said: "...He who embraces a woman who is unlawful (haram) to him, will be bound by a chain of fire alongwith Satan and both will be thrown into Hell."
Man La Yahduruhul Faqih, vol. 4, p. 14
Once, 'Ammar ibn Musa asked Imam Sadiq [a] about commiting sexual intercourse with beasts or masterbation by the hand or other limbs of one's ownself, and he [a] replied: "Any form of these kinds and the like of them by which man pours forth his water, is (considered as) fornication (and it is unlawful)."
AI-Kafi, vol. 5, p. 541
The Holy Prophet [s] said: "Cursed is he, cursed is he who copulates with beasts."
AI-Kafi, vol. 2, p. 270
The Holy Prophet [s] said: "Lesbianism between themselves is (the same as) fornication."
Kanz-ul-'Ummal, vol. 5, p. 316