Sunan Abu Dawud
3440
Sahih+2

Narrated Anas ibn Malik: 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

SahihAl-Albani
SahihMuhammad Muhyi Al-Din Abdul Hamid