Musannaf Ibn Abi Shayba 18:1260

Abu Bakr narrated to us, he said: Muhammad ibn Yazid narrated to us, from Abu al-Ala, from Qatadah and Abu Hashim. They both said regarding a man who killed another man intentionally, so he was imprisoned to be executed in retaliation for him, then a man came and killed him intentionally: They both said, "He shall not be executed in retaliation for him."