Hadith 2.1
Retaliation
Sahl b. Sa'd said that a man looked through a hole in God’s Messenger’s door when God’s Messenger had a spike with which he was scratching his head, so he said, “If I knew that you were seeing me I would poke it in your eyes, for asking permission has been appointed only on account of what people may see.” (Bukhari and Muslim.)
وَعَن سهل بنِ سعد: أَنَّ رَجُلًا اطَّلَعَ فِي جُحْرٍ فِي بَابِ رَسُولِ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ وَمَعَ رَسُولِ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ مِدْرًى يَحُكُّ بِهِ رَأْسَهُ فَقَالَ: «لَوْ أَعْلَمُ أَنَّكَ تنظُرُني لطَعَنْتُ بهِ فِي عَيْنَيْكَ إِنَّمَا جُعِلَ الِاسْتِئْذَانُ مِنْ أَجْلِ الْبَصَرِ»
Hadith gradings, numbering and translations can differ between editions. For legal rulings or detailed interpretation, consult qualified scholarship and the referenced edition.