A man peeped into the house of the Prophet ﷺ through a hole while the Prophet ﷺ was scratching his head with a Midrai (a certain kind of comb). On that the Prophet ﷺ 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."  

أَنَّ رَجُلاً اطَّلَعَ مِنْ جُحْرٍ فِي دَارِ النَّبِيِّ ﷺ وَالنَّبِيُّ ﷺ يَحُكُّ رَأْسَهُ بِالْمِدْرَى فَقَالَ لَوْ عَلِمْتُ أَنَّكَ تَنْظُرُ لَطَعَنْتُ بِهَا فِي عَيْنِكَ إِنَّمَا جُعِلَ الإِذْنُ مِنْ قِبَلِ الأَبْصَارِ  

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 through a hole in the door of Messenger of Allah ﷺ's house, and at that time, Messenger of Allah ﷺ had a Midri (an iron comb or bar) with which he was rubbing his head. So when Messenger of Allah ﷺ 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)." Messenger of Allah ﷺ 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)."  

أَخْبَرَهُ أَنَّ رَجُلاً اطَّلَعَ فِي جُحْرٍ فِي باب رَسُولِ اللَّهِ ﷺ وَمَعَ رَسُولِ اللَّهِ ﷺ مِدْرًى يَحُكُّ بِهِ رَأْسَهُ فَلَمَّا رَآهُ رَسُولُ اللَّهِ ﷺ قَالَ لَوْ أَعْلَمُ أَنْ تَنْتَظِرَنِي لَطَعَنْتُ بِهِ فِي عَيْنَيْكَ قَالَ رَسُولُ اللَّهِ ﷺ إِنَّمَا جُعِلَ الإِذْنُ مِنْ قِبَلِ الْبَصَرِ  

If I were to know that you had been peeping through the door, I would have thrust that into your eyes, and Messenger of Allah ﷺ said: Permission is needed as a protection against glance.  

أَخْبَرَهُ أَنَّ رَجُلاً اطَّلَعَ فِي جُحْرٍ فِي بَابِ رَسُولِ اللَّهِ ﷺ وَمَعَ رَسُولِ اللَّهِ ﷺ مِدْرًى يَحُكُّ بِهِ رَأْسَهُ فَلَمَّا رَآهُ رَسُولُ اللَّهِ ﷺ قَالَ لَوْ أَعْلَمُ أَنَّكَ تَنْظُرُنِي لَطَعَنْتُ بِهِ فِي عَيْنِكَ وَقَالَ رَسُولُ اللَّهِ ﷺ إِنَّمَا جُعِلَ الإِذْنُ مِنْ أَجْلِ الْبَصَرِ  

a man looked through a hole in the door of the Prophet, who had with him a kind of comb with which he was scratching his head, When the Messenger of Allah saw him he said: "If I had known that you were watching me, I would have stabbed you in the eye with this. This rule of asking permission has been ordained so that one may not look unlawfully (into people's houses).  

أَخْبَرَهُ أَنَّ رَجُلاً اطَّلَعَ مِنْ جُحْرٍ فِي بَابِ رَسُولِ اللَّهِ ﷺ وَمَعَ رَسُولِ اللَّهِ ﷺ مِدْرَى يَحُكُّ بِهَا رَأْسَهُ فَلَمَّا رَآهُ رَسُولُ اللَّهِ ﷺ قَالَ لَوْ عَلِمْتُ أَنَّكَ تَنْظُرُنِي لَطَعَنْتُ بِهِ فِي عَيْنِكَ إِنَّمَا جُعِلَ الإِذْنُ مِنْ أَجْلِ الْبَصَرِ