From Sayyiduna Abu Yazid (may Allah be pleased with him), his son Hakim narrates that the Messenger of Allah (peace and blessings be upon him) said: "A town-dweller should not sell for a desert-dweller (that is, should not act as his broker). Leave the people so that they may benefit from one another, and when a man seeks advice from his brother, let him advise him sincerely."
Imam al-Tabarani (may Allah have mercy on him) said: This is how Mansur bin Abi al-Aswad narrated it from Hakim bin Abi Yazid, and in this hadith he added to the narration of the others: "A town-dweller should not sell for a desert-dweller."
Hadith Referenceالمعجم الكبير للطبراني / مسند من يعرف بالكنى / 19094