(17, 18) باب الْقِصَاصِ مِنَ الثَّنِيَّةِ
Anas narrated that:
his paternal aunt broke the front tooth of a girl and the Prophet of Allah decreed retaliation. Her brother, Anas bin An-Nadr, said: "Will you break the front tooth of so and so? No, by the One Who sent you with the truth, the front tooth of so and so will not be broken!" Before that, they had asked her family for forgiveness and blood money. When her brother - who was the paternal uncle of Anas and was martyred at Uhud - swore that oath, the people agreed to forgive. The Prophet said: "There are among the slaves of Allah who, if they swear by Allah, Allah fulfills their oath."
Reference: Sunan an-Nasa'i 4756
In-book reference: Book 45, Hadith 51
English translation: Vol. 5, Book 45, Hadith 4760