Sahih Muslim 2158 b
Abu Huraira reported Allah's Messenger (ﷺ) as saying:
If a person were to cast a glance in your (house) without permission, and you had in your hand a staff and you would have thrust that in his eyes, there is no harm for you.
حَدَّثَنَا ابْنُ أَبِي عُمَرَ، حَدَّثَنَا سُفْيَانُ، عَنْ أَبِي الزِّنَادِ، عَنِ الأَعْرَجِ، عَنْ أَبِي هُرَيْرَةَ،
 أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ ‏
"‏ لَوْ أَنَّ رَجُلاً اطَّلَعَ عَلَيْكَ بِغَيْرِ إِذْنٍ فَخَذَفْتَهُ
 بِحَصَاةٍ فَفَقَأْتَ عَيْنَهُ مَا كَانَ عَلَيْكَ مِنْ جُنَاحٍ ‏"‏ ‏.‏