Riyad as-Salihin 1622
The Book of the Prohibited actions
Prohibition of gazing at women and Beardless Handsome Boys except in Exigency
Abu Hurairah (May Allah be pleased with him) said: The Prophet (ﷺ) said, "Allah has written the very portion of Zina which a man will indulge in. There will be no escape from it. The Zina of the eye is the (lustful) look, the Zina of the ears is the listening (to voluptuous songs or talk), the Zina of the tongue is (the licentious) speech, the Zina of the hand is the (lustful) grip, the Zina of the feet is the walking (to the place where he intends to commit Zina), the heart yearns and desires and the private parts approve all that or disapprove it." [Al-Bukhari and Muslim]. This is the wording in Muslim; Al-Bukhari wording is a bit short.