Anas bin Malik (May Allah be pleased with him) said:
The Messenger of Allah ﷺ forbade that a person in the city should make a deal on behalf of a villager on commission even if he is his real brother."

[Al-Bukhari and Muslim].

عن أنس رضي الله عنه قال: نهى رسول الله ﷺ أن يبيع حاضر لباد وإن كان أخاه لأبيه وأمه. ((متفق عليه)).