Musnad Abu Ya'la al-Mawsili 117:122

Ibrahim ibn al-Hajjaj al-Sami narrated to us, Hammad narrated to us, from Thabit, from Anas, that the sister of al-Rubayyi', the mother of Harithah, wounded a person. The Messenger of Allah (peace and blessings of Allah be upon him) said: "Retaliation, retaliation." The mother of al-Rubayyi' said: "O Messenger of Allah, shall retaliation be taken from so-and-so? No, by Allah, retaliation shall not be taken from her." The Prophet (peace and blessings of Allah be upon him) said: "Subhan Allah, O mother of al-Rubayyi', retaliation is the Book of Allah." She said: "No, by Allah, retaliation shall never be taken from her." The Messenger of Allah (peace and blessings of Allah be upon him) said: "Indeed, among the servants of Allah are those who, if they were to swear by Allah, He would fulfill it for them."