Sahih al-Bukhari 4611
Sahih al-Bukhari · Book 65: Prophetic Commentary on the Qur'an (Tafseer of the Prophet (pbuh)) · Allah's Statement: "...And wounds, equal for equal (A1-Qisas i.e., the law of equality in punishment)..." (V.5:45)
Narrated Anas (bin Malik):
حَدَّثَنِي مُحَمَّدُ بْنُ سَلاَمٍ ، أَخْبَرَنَا الْفَزَارِيُّ ، عَنْ حُمَيْدٍ ، عَنْ أَنَسٍ ـ رضى الله عنه ـ قَالَ كَسَرَتِ الرُّبَيِّعُ ـ وَهْىَ عَمَّةُ أَنَسِ بْنِ مَالِكٍ ـ ثَنِيَّةَ جَارِيَةٍ مِنَ الأَنْصَارِ، فَطَلَبَ الْقَوْمُ الْقِصَاصَ، فَأَتَوُا النَّبِيَّ صلى الله عليه وسلم فَأَمَرَ النَّبِيُّ صلى الله عليه وسلم بِالْقِصَاصِ. فَقَالَ أَنَسُ بْنُ النَّضْرِ عَمُّ أَنَسِ بْنِ مَالِكٍ لاَ وَاللَّهِ لاَ تُكْسَرْ سِنُّهَا يَا رَسُولَ اللَّهِ. فَقَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " يَا أَنَسُ كِتَابُ اللَّهِ الْقِصَاصُ ". فَرَضِيَ الْقَوْمُ وَقَبِلُوا الأَرْشَ فَقَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " إِنَّ مِنْ عِبَادِ اللَّهِ مَنْ لَوْ أَقْسَمَ عَلَى اللَّهِ لأَبَرَّهُ " .
Ar-Rubai (the paternal aunt of Anas bin Malik) broke the incisor tooth of young Ansari girl. Her family demanded the Qisas and they came to the Prophet (ﷺ) who passed the judgment of Qisas. Anas bin An-Nadr (the paternal uncle of Anas bin Malik) said, "O Allah's Messenger (ﷺ)! By Allah, her tooth will not be broken." The Prophet (ﷺ) said, "O Anas! (The law prescribed in) Allah's Book is Qisas." But the people (i.e. the relatives of the girl) gave up their claim and accepted a compensation. On that Allah's Apostle said, "Some of Allah's worshippers are such that if they take an oath, Allah will fulfill it for them."