The Prophet (ﷺ) said: A townsman must not sell for a man from the desert, even if he is his brother or father.

Abu Dawud said: Anas b. Malik said: It was said: A townsman must not sell for a man from the desert. This phrase carries a broad meaning. It means that the (the townsman) must not sell anything for him or buy anything for him.
Sunan Abi Dawud Book 24, Hadith 25
← Previous Hadith The Messenger of Allah (ﷺ) forbade a townsman to sell for a man from the desert. I asked: What do you mean by the selling of a townsman for a man from the desert ? He replied: He should not be a broker for him.

Sunan Abi Dawud Book 24, Hadith 24 Next Hadith → That a bedouin told him that he brought a milch she-camel in the time of the Messenger of Allah (ﷺ). He alighted with Talhah ibn Ubaydullah (and wanted to sell his milch animal to him). He said: The Prophet (ﷺ) forbade a townsman to sell for a man from the desert. But go to the market and see who buys from you. consult me thereafter, and then I shall ask you (to sell) or forbid you.

Sunan Abi Dawud Book 24, Hadith 26