If a person attacks another person's life and limb, and the other defends himself and kills him or injures him, there is no penalty on him
حَدَّثَنِي أَبُو غَسَّانَ الْمِسْمَعِيُّ، حَدَّثَنَا مُعَاذٌ، - يَعْنِي ابْنَ هِشَامٍ - حَدَّثَنِي أَبِي، عَنْ قَتَادَةَ، عَنْ زُرَارَةَ بْنِ أَوْفَى، عَنْ عِمْرَانَ بْنِ حُصَيْنٍ، أَنَّ رَجُلاً، عَضَّ ذِرَاعَ رَجُلٍ فَجَذَبَهُ فَسَقَطَتْ ثَنِيَّتُهُ فَرُفِعَ إِلَى النَّبِيِّ صلى الله عليه وسلم فَأَبْطَلَهُ وَقَالَ " أَرَدْتَ أَنْ تَأْكُلَ لَحْمَهُ " .
'Imran b. Husain reported that a person bit the arm of another person; he pulled it out and his foretooth fell down. This matter was taken to Allah's Messenger (ﷺ), and he turned it down saying: Did you want to eat his flesh?