Sahih Muslim Book - 38, Hadith - 5638

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 اللهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ ، وَمَعَ رَسُولِ اللهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ مِدْرًى يَحُكُّ بِهِ رَأْسَهُ ، فَلَمَّا رَآهُ رَسُولُ اللهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ : لَوْ أَعْلَمُ أَنَّكَ تَنَْظِرُنِي لَطَعَنْتُ بِهِ فِي عَيْنِكَ وَقَالَ رَسُولُ اللهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ : إِنَّمَا جُعِلَ الإِذْنُ مِنْ أَجْلِ الْبَصَرِ.

Sahl bin Sa'd As-Sa'idi narrated that a man looked through a crack in the door of the Messenger of Allah (s.a.w), and the Messenger of Allah (s.a.w) had a comb with which he was scratching his head. When the Messenger of Allah (s.a.w) saw him he said: "If I had known that you were looking at me I would have poked you in the eye with it." And the Messenger of Allah (s.a.w) said: "Seeking permission is enjoined because of looking."