Musannaf Ibn Abi Shayba 18:36

Abu Bakr narrated to us, he said: Jarir narrated to us, from Mughira, from al-Sha’bi, who said: Abu Musa and al-Mughira ibn Shu’bah used to say regarding the aggravated (manslaughter): Its blood money is thirty hiqqah (three-year-old camels), thirty jadha’ah (four-year-old camels), and forty khalifah (pregnant camels), ranging from a thaniyyah (five-year-old camel) to a bazil (six-year-old camel), all of which are pregnant.