Amr bin Shu'ayb narrates from his father, and he from his grandfather (may Allah be pleased with him), that the Prophet (peace and blessings be upon him) said: "Whoever commits deliberate killing, the killer is to be handed over to the heirs of the slain; they may take retaliation if they wish, or blood money." And in the hadith of Sayyiduna Wa'il bin Hujr (may Allah be pleased with him) it is that a killer was brought to the Prophet (peace and blessings be upon him), and he (peace and blessings be upon him) asked the heir of the slain: "Do you pardon him?" He said: No. He (peace and blessings be upon him) asked: "Will you take blood money?" He said: No. He (peace and blessings be upon him) asked: "Will you kill him?" He said: Yes. He (peace and blessings be upon him) said: "Very well, take him away."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنايات / 16043