Ibn 'Abbas (May Allah be pleased with them) said:
The Messenger of Allah ﷺ said, "The caravans carrying merchandise should not be met on the way to purchase from them; a man in the city should not sell for a man of the desert."

Tawus asked him (Ibn 'Abbas): "What do these words really imply?" He said: "He should not work as an agent on his behalf."

[Al-Bukhari and Muslim].

وعن ابن عباس رضي الله عنهما قال: قال رسول الله ﷺ : “لا تتلقوا الركبان، ولا يبع حاضر لباد" فقال له طاوس: ما قوله: لا بيع حاضر لباد؟ قال: لا يكون له سمسارًا. ((متفق عليه)).