Musannaf Ibn Abi Shayba 18:41

Abu Bakr narrated to us, he said: Abd al-A’la narrated to us, from Yunus, from al-Hasan, regarding the severe penalty: Forty pregnant camels, from those that have entered their second year (thaniyah) up to those that have reached their ninth year (bazil), for quasi-intentional homicide, regarding the ages of the camels.