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)  

الزُّهْرِيُّ حَفِظْتُهُ كَمَا أَنَّكَ هَا هُنَا عَنْ سَهْلِ بْنِ سَعْدٍ قَالَ اطَّلَعَ رَجُلٌ مِنْ جُحْرٍ فِي حُجَرِ النَّبِيِّ ﷺ وَمَعَ النَّبِيِّ ﷺ مِدْرًى يَحُكُّ بِهِ رَأْسَهُ فَقَالَ لَوْ أَعْلَمُ أَنَّكَ تَنْظُرُ لَطَعَنْتُ بِهِ فِي عَيْنِكَ إِنَّمَا جُعِلَ الاِسْتِئْذَانُ مِنْ أَجْلِ الْبَصَرِ  

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.  

أَنَّ رَجُلاً اطَّلَعَ مِنْ بَعْضِ حُجَرِ النَّبِيِّ ﷺ فَقَامَ إِلَيْهِ النَّبِيُّ ﷺ بِمِشْقَصٍ أَوْ بِمَشَاقِصَ فَكَأَنِّي أَنْظُرُ إِلَيْهِ يَخْتِلُ الرَّجُلَ لِيَطْعُنَهُ