Say to the believing men that they should lower their gaze and guard their modesty: that will make for greater purity for them: And Allah is well acquainted with all that they do.
The Prophet (peace be on him) considered hungry and lustful looks at a person of the opposite sex as “the zina of the eye,” according to his saying, “The eyes also commit zina, and their zina is the lustful look.” (Reported by al-Bukhari and others.)
He termed the lustful look zina because it gives sexual pleasure and gratification in an unlawful way.
This is also what Jesus (peace be on him) is reported to have said in the Gospel of Matthew: You have heard that it was said, ‘You shall not commit adultery’. But I say to you that everyone who so much as looks at woman with evil desire for her has already committed adultery with her in his heart. (Matt. 5:2728)
Al-Qaradawi, Yusuf (1960). The Lawful and Prohibited in Islam. (p. 149-150). http://www.islamicweblibrary.com/wp-content/uploads/2019/06/TheLawfulAndTheProhibitedInIslamal-halalWalHaramFilIslamByShaykhYusufAlQardawi.pdf