It was narrated that Anas said:"Ar-Rubai broke the front tooth of a girls, and they asked them (her people) to forgive her, but they refused. They offered them blood money, but they refused. Then they went to the Prophet and he decreed relation. Anas Bin An-Nadr said: "O Messenger of Allah, will you break the front tooth of Ar-Rubai'? No, by the One Who sent you with the truth, it will not be broken!" He said: "O Anas, what Allah has decreed is retaliation." But the people agreed to forgive her. He (the Prophet) said: "There are among the slaves of Allah who, if they swear by Allah, Allah fulfills their oath."
أَخْبَرَنَا مُحَمَّدُ بْنُ الْمُثَنَّى، قَالَ حَدَّثَنَا خَالِدٌ، قَالَ حَدَّثَنَا حُمَيْدٌ، عَنْ أَنَسٍ، قَالَ كَسَرَتِ الرُّبَيِّعُ ثَنِيَّةَ جَارِيَةٍ فَطَلَبُوا إِلَيْهِمُ الْعَفْوَ فَأَبَوْا فَعُرِضَ عَلَيْهِمُ الأَرْشُ فَأَبَوْا فَأَتَوُا النَّبِيَّ صلى الله عليه وسلم فَأَمَرَ بِالْقِصَاصِ . قَالَ أَنَسُ بْنُ النَّضْرِ يَا رَسُولَ اللَّهِ تُكْسَرُ ثَنِيَّةُ الرُّبَيِّعِ لاَ وَالَّذِي بَعَثَكَ بِالْحَقِّ لاَ تُكْسَرُ . قَالَ " يَا أَنَسُ كِتَابُ اللَّهِ الْقِصَاصُ " . فَرَضِيَ الْقَوْمُ وَعَفَوْا فَقَالَ " إِنَّ مِنْ عِبَادِ اللَّهِ مَنْ لَوْ أَقْسَمَ عَلَى اللَّهِ لأَبَرَّهُ " .
Nesai
The Book of Oaths (qasamah), Retaliation and Blood Money • Hadith 4757