Sahih al-Bukhari 6241

Ali ibn Abdullah narrated to us: Sufyan narrated to us. Al-Zuhri said: I remember it as clearly as I see you here, from Sahl ibn Sad, who said: A man peered through a hole into one of the Prophet’s rooms. The Prophet, peace and blessings be upon him, had an iron comb in his hand with which he was scratching his head. He said, ‘Had I known you were looking, I would have pierced your eye with it. Permission to enter was prescribed because of the gaze.’