Musnad Ahmad 799:42

'Ali ibn 'Abdullah narrated to us, Mu'adh narrated to us, my father narrated to me, from Matar, from al-Hasan, from Samurah: "The Prophet of Allah, peace and blessings of Allah be upon him, forbade that the caravans (bringing goods) be met (outside the city) until they reach the markets, or that a resident sell on behalf of a bedouin."