Musannaf Ibn Abi Shayba 13:2105

Abu Bakr narrated to us, he said: Abd al-Razzaq narrated to us, from Ma'mar, from Ibn Tawus, from his father, who said: I said to Ibn Abbas, "What is [the meaning of] 'a resident should not sell for a bedouin'?" He said, "He should not be a broker for him."