Musannaf Ibn Abi Shayba 18:47

Abu Bakr narrated to us, he said: Muhammad ibn Mus'ab narrated to us, from al-Awza'i, from al-Zuhri, who said: "Quasi-intentional (shibh al-'amd) is that a man strikes a man due to a blood feud that is between them, and he does not intend to kill him, but he becomes ill because of that and dies."