Volume 3, Book 49, Number 866 :
Narrated by Anas (radiallaahu `anhu)
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 Arsh (الأَرْشَ) (compensation for wounds etc.) and forgive (the offender), but they refused. So, they went to the Prophet (sallallaahu `alayhi wasallam) who ordered them to bring about retaliation. Anas bin An-Nadr (radiallaahu `anhu) asked, “O Allah’s 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 (sallallaahu `alayhi wasallam) said, “O Anas! Allah’s law ordains retaliation.” Later the relatives of the girl agreed and forgave her. The Prophet (sallallaahu `alayhi wasallam) 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 (radiallaahu `anhu) added, “The people agreed and accepted the Arsh.”
There was another post about breaking someone’s teeth a while ago in which Prophet (sallallaahu `alayhi wasallam) ruled in favor of the defender since he broke the other’s tooth while fending for himself.
In this case, however, the defender was given the choice to either forgive Rabi` (offender), accept Arsh (compensation) or to get qisaas (retaliation). Prophet (sallallaahu `alayhi wasallam) would have made sure that qisaas took place had they not forgiven Rabi`. Allah’s laws are just and perfectly fit to be implemented.
Abu Shurayh al-Khuzaa’i said: The Messenger of Allaah (peace and blessings of Allaah be upon him) said: “Whoever is killed or is wounded, has the choice of three things, and if he wants the fourth then restrain him. He may kill (the killer), or forgive him, or take the diyah (blood money).” Narrated by Abu Dawood.