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.)
Hadith Referenceمشكوة المصابيح / كتاب القصاص / 3515
Hadith Gradingالألبانی:مُتَّفق عَلَيْهِ | زبیر علی زئی:متفق عليه
Hadith Takhrij´تحقيق و تخريج: محدث العصر حافظ زبير على زئي رحمه الله` «متفق عليه، رواه البخاري (6901) و مسلم (40/ 2156)»