Bukhari :: Book 7 :: Volume 72 :: Hadith 807
A man peeped into the house of the Prophet through a hole while the Prophet was scratching his head with a Midrai (a certain kind of comb). On that the Prophet said (to him), "If I had known you had been looking, then I would have pierced your eye with that instrument, because the asking of permission has been ordained so that one would not see things unlawfully."
Source materials are from the University of Southern California MSA site|
Hadith eBooks converted from Imaan Star