Sahih Muslim , Book 25, Hadith 5366 (USC-MSA) ⓘ

Sahl b. Sa'd as-Sa'id reported that a person peeped through the hole of the door of Allah's Messenger, and at that time Allah's Messenger had with him a scratching instrument with which he had been scratching his head. When Allah's Messenger saw him. he said: If I were to know that you had been peeping through the door, I would have thrust that into your eyes, and Allah's Messenger said: Permission is needed as a protection against glance.

حَدَّثَنَا يَحْيَى بْنُ يَحْيَى، وَمُحَمَّدُ بْنُ رُمْحٍ، قَالاَ أَخْبَرَنَا اللَّيْثُ، - وَاللَّفْظُ لِيَحْيَى - ح وَحَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، حَدَّثَنَا لَيْثٌ، عَنِ ابْنِ شِهَابٍ، أَنَّ سَهْلَ بْنَ سَعْدٍ السَّاعِدِيَّ، أَخْبَرَهُ أَنَّ رَجُلاً اطَّلَعَ فِي جُحْرٍ فِي بَابِ رَسُولِ اللَّهِ صلى الله عليه وسلم وَمَعَ رَسُولِ اللَّهِ صلى الله عليه وسلم مِدْرًى يَحُكُّ بِهِ رَأْسَهُ فَلَمَّا رَآهُ رَسُولُ اللَّهِ صلى الله عليه وسلم قَالَ ‏"‏ لَوْ أَعْلَمُ أَنَّكَ تَنْظُرُنِي لَطَعَنْتُ بِهِ فِي عَيْنِكَ ‏"‏ ‏.‏ وَقَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏"‏ إِنَّمَا جُعِلَ الإِذْنُ مِنْ أَجْلِ الْبَصَرِ ‏"‏ ‏.‏