Musannaf Ibn Abi Shayba 18:528

Abu Bakr narrated to us, he said: Bahz ibn Asad narrated to us, from Aban al-Attar, from Qatadah, from Sa’id ibn al-Musayyib regarding a man whom a group kills. He said: They may kill whomever they wish, and they may pardon whomever they wish, and they may take the blood money from whomever they wish.