A town dweller should not buy goods for a desert dweller and charge commission as a broker Sahih al-Bukhari 2161
Arabic hadith text
حَدَّثَنَا مُحَمَّدُ بْنُ الْمُثَنَّى، حَدَّثَنَا مُعَاذٌ، حَدَّثَنَا ابْنُ عَوْنٍ، عَنْ مُحَمَّدٍ، قَالَ أَنَسُ بْنُ مَالِكٍ ـ رضى الله عنه ـ نُهِينَا أَنْيَبِيعَ حَاضِرٌ لِبَادٍ.
Translation
Narrated Anas bin Malik
We were forbidden that a town dweller should sell goods of a desert dweller.