Musannaf Ibn Abi Shayba 13:835

Abu Bakr narrated to us, he said: Abbad ibn al-Awwam narrated to us, from Hajjaj, from al-Hakam, from Ibn Mughaffal, he said: Do not buy anything from the land of as-Sawad except from the people of Baniqya, the people of al-Hira, and the people of Alis.