Musannaf Ibn Abi Shayba 28:994

Waki’ narrated to us, he said: Ibn ‘Awn narrated to us, from Ghadirah al-‘Anbari, he said: We came to ‘Umar. Ibn ‘Awn said: He either said regarding women or he said regarding your slave women who were sold during the Jahiliyyah (pre-Islamic period), so he ordered that their children be attributed to their fathers and that they should not be enslaved.