Maliks Muwatta Book 43, Hadith Number 15C.
Yahya related to me from Malik that he saw whomever he was satisfied with among the people of knowledge say about a man who willed that his murderer be pardoned when he murdered him intentionally, “That is permitted for him. He is more entitled to the man’s blood than any of his relatives after him.”
Malik said about a man who pardoned murder, after he had claimed his right and it was obliged for him, “There is no blood-money against the murderer unless the one who pardons him stipulates that when he pardons him.”
Malik said about the murderer when he was pardoned, “He is flogged one hundred lashes and jailed for a year.”
Malik said, “When a man murders intentionally and there is a clear proof of that, and the murdered man has sons and daughters and the sons pardon and the daughters refuse to pardon, the pardon of the sons is permitted in opposition to the daughters and there is no authority for the daughters with the sons in demanding blood and pardoning.”