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. (Using translation from Abū Dāʾūd 3440)
عَنِ النَّبِيِّ ﷺ قَالَ لَا يَبِيعُ حَاضِرٌ لِبَادٍ وَإنْ كَانَ أَخَاهُ أَوْ أَبَاهُ