A man peeped into a room of the Prophet. The Prophet (ﷺ) stood up, holding an arrow head. It is as if I am just looking at him, trying to stab the man.
Sahih al-Bukhari Book 79, Hadith 16
← Previous Hadith A man peeped through a round hole into the dwelling place of the Prophet, while the Prophet (ﷺ) had a Midray (an iron comb) with which he was scratching his head. the Prophet (ﷺ) said, " Had known you were looking (through the hole), I would have pierced your eye with it (i.e., the comb)." Verily! The order of taking permission to enter has been enjoined because of that sight, (that one should not look unlawfully at the state of others). (See Hadith No. 807, Vol. 7)

Sahih al-Bukhari Book 79, Hadith 15 Next Hadith → I have not seen a thing resembling 'lamam' (minor sins) than what Abu Huraira 'narrated from the Prophet who said "Allah has written for Adam's son his share of adultery which he commits inevitably. The adultery of the eyes is the sight (to gaze at a forbidden thing), the adultery of the tongue is the talk, and the inner self wishes and desires and the private parts testify all this or deny it."

Sahih al-Bukhari Book 79, Hadith 17