Sunan An-Nasa'i

It was narrated from Anas that:the sister of Ar-Rubai' Umm Harithah injured a person and they referred the dispute to the Messenger of Allah. The Messenger of Allah said: ""Retaliation, retaliation (Qisas)."" Umm Ar-Rabi said: 'O Messenger of Allah, how could retaliation be carried out against so and so? No, by Allah, retaliation willnever be carried out against her!' The Messenger of Allah said: ""Subhan Allah, O Umm Ar-Rabi'! decreed by Allah."" She said: ""No, by Allah, retaliation will never be carried out against her!"" And she carried on until they accepted Diyah (blood money). He (the prophet) said: ""There are among the slaves of Allah who, if they swear by Allah, Allah fulfills their oath