It was narrated that Ibn ‘Abbas said: “There was Qisas among the Children of Israel, but Diyah was unknown among them. Then Allah, the Mighty and Sublime, revealed: Al-Qi (the law of equality in punishment) is prescribed for you in case of murder: the free for the free, the slave for the slave, and the female for the female..” up to His saying:
“But if the killer is forgiven by the brother (or the relatives) of the killed against blood money, then adhering to it with fairness and payment of the blood money to the heir should be made in fairness.” Forgiveness means accepting the Diyah in the case of deliberate killing. Adhering to it in fairness means asking him to pay the Diyah in a fair manner, and payment in fairness means giving the Diyah in a fair manner. This is an alleviation and a mercy from your Lord, means: This is easier than that which was prescribed for those who came before you, which was Qisas and not Diyah.” (Sahih)