Mukhtasar Bukhari

Narrated Ibn Abbas (may Allah be pleased with them) that the Messenger of Allah (peace and blessings of Allah be upon him) said: "Do not meet the caravans bringing grain on the way, but let them come to the town, and no townsman should sell for a (Bedouin) outsider." Ibn Abbas (may Allah be pleased with them) was asked, "What does it mean that no townsman should sell for an outsider?" He replied, "It means that he should not act as a broker for him."