Musannaf Ibn Abi Shayba 7:126

Abu Bakr narrated to us, he said: Hushaym ibn Bashir narrated to us, from Yunus, from al-Hasan, and [from] Mughirah, from Ibrahim, and [from] Hajjaj, from ‘Ata’, that they said regarding the one who causes the loss of a fetus: "Upon him is the freeing of a slave along with the *ghurra* (compensation)."