Musnad Ahmad 346

Abu al-Mundhir—Isma‘il ibn ‘Umar, as I suppose—from Hajjaj, from ‘Amr ibn Shu‘ayb, from his father, from his grandfather, who said: A man deliberately killed his son and was brought before ‘Umar ibn al-Khattab, may Allah be pleased with him. ‘Umar imposed on him one hundred camels: thirty mature she-camels in their fourth year, thirty in their fifth year, and forty older she-camels. He said, ‘The killer does not inherit. Were it not that I heard the Messenger of Allah, peace and blessings be upon him, say, “A parent is not killed in retaliation for their child,” I would have killed you.’