It was narrated from Ya'la bin Munyah that:he fought a man and one of them bit the other, who pulled his forearm away from his mouth, and a front tooth fell out. The matter was referred to the Prophet and he said: "Would one of you bite his brother as a young camel bites?" And judged it to be invalid.
أَخْبَرَنَا مَالِكُ بْنُ الْخَلِيلِ، قَالَ حَدَّثَنَا ابْنُ أَبِي عَدِيٍّ، عَنْ شُعْبَةَ، عَنِ الْحَكَمِ، عَنْ مُجَاهِدٍ، عَنْ يَعْلَى ابْنِ مُنْيَةَ، أَنَّهُ قَاتَلَ رَجُلاً فَعَضَّ أَحَدُهُمَا صَاحِبَهُ فَانْتَزَعَ يَدَهُ مِنْ فِيهِ فَقَلَعَ ثَنِيَّتَهُ فَرُفِعَ ذَلِكَ إِلَى النَّبِيِّ صلى الله عليه وسلم فَقَالَ " يَعَضُّ أَحَدُكُمْ أَخَاهُ كَمَا يَعَضُّ الْبَكْرُ " . فَأَبْطَلَهَا .
Nesai
The Book of Oaths (qasamah), Retaliation and Blood Money • Hadith 4763