Volume 7, Book 72, Number 807:
Narrated Sa’d:
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.”