What did the Prophet Muhammad (saw) do when he noticed someone had looked through a hole into his house without permission?
      Narrated Sahl bin Sa'd As-Sa'idi:                          A man peeped through a hole in the door of Allah's Apostle's house,      and at that time, Allah's Apostle had a Midri (an iron comb or bar)      with which he was rubbing his head. So when Allah's Apostle saw him,      he said (to him), "If I had been sure that you were looking at me      (through the door), I would have poked your eye with this (sharp iron      bar)." Allah's Apostle added, "The asking for permission to enter has      been enjoined so that one may not look unlawfully (at what there is in     the house without the permission of its people)."