Sahih Bukhari Volume 3, Book 49, Number 866:
Narrated Anas: Ar-Rabi, the daughter of An-Nadr broke the tooth of a girl, and the relatives of Ar-Rabi’ requested the girl’s relatives to accept the Irsh (compensation for wounds etc.) and forgive (the offender), but they refused. So, they went to the Prophet who ordered them to bring about retaliation. Anas bin An-Nadr asked, “O Allah”; Apostle! Will the tooth of Ar-Rabi’ be broken? No, by Him Who has sent you with the Truth, her tooth will not be broken.” The Prophet said, “O Anas! Allah”; law ordains retaliation.” Later the relatives of the girl agreed and forgave her. The Prophet said, “There are some of Allah’s slaves who, if they take an oath by Allah, are responded to by Allah i.e. their oath is fulfilled). Anas added, “The people agreed and accepted the Irsh.”

Sahih Bukhari Volume 3, Book 49, Number 866:
Ar-Rabi, the daughter of An-Nadr who was a young girl had broken a tooth of another girl and the other girl’s relatives had asked for retaliation instead of compensation

Here a few points noting, The Holy Prophet Muhammed Salalaahu Alaihi wasallam took an OATH that the young girl’s tooth will not be broken

“No, by Him Who has sent you with the Truth, her tooth will not be broken”

and later than it so happened that the relatives of the other girl agreed to take money instead of retaliation after the Holy Prophet took the OATH by Allah, so the Holy Prophet Muhammed Salalaahu Alaihi wasallam’s OATH was fulfilled, and then he said
“There are some of Allah’s slaves who, if they take an oath by Allah, are responded to by Allah i.e. their oath is fulfilled)”