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]. (DE)
App reference (DE): Book 18, Hadith 267 (DE)
Arabic/English book reference (DE): Book 18, Hadith 1777 (DE)