Mishkat al-Masabih 3511
Ya’ la b. Umayya said:
I went with God’s Messenger on the expedition of the army of distress,* and I had a hired servant who fought with a man, one of whom bit the other’s hand. The one who was bitten drew away his hand from the mouth of the one who bit him, dislodging his front tooth which fell out. He went to the Prophet, but he imposed no retaliation for his front tooth, saying, ‘Could he be expected to leave his hand in your mouth when you were crunching it like a male camel?” 

(Bukhari and Muslim.)

* This refers to the expedition to Tabuk in 9 A H. Cf. Al-Qur'an, 9:117.
وَعَنْ يَعْلَى بْنِ أُمَيَّةَ قَالَ: غَزَوْتُ مَعَ رَسُولِ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ جَيْشَ الْعُسْرَةِ وَكَانَ لِي أَجِيرٌ فقاتلَ إِنساناً فعض أَحدهمَا الْآخَرِ فَانْتَزَعَ الْمَعْضُوضُ يَدَهُ مِنْ فِي الْعَاضِّ فَأَنْدَرَ ثَنِيَّتَهُ فَسَقَطَتْ فَانْطَلَقَ إِلَى النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ فَأَهْدَرَ ثَنِيَّتَهُ وَقَالَ: «أَيَدَعُ يَدَهُ فِي فِيكَ تَقْضِمُهَا كَالْفَحْلِ»