It is forbidden to meet the caravans on the way (to buy the goods away from the market)
حَدَّثَنِي عَيَّاشُ بْنُ الْوَلِيدِ، حَدَّثَنَا عَبْدُ الأَعْلَى، حَدَّثَنَا مَعْمَرٌ، عَنِ ابْنِ طَاوُسٍ، عَنْ أَبِيهِ، قَالَ سَأَلْتُ ابْنَ عَبَّاسٍ ـ رضى الله عنهما ـ مَا مَعْنَى قَوْلِهِ " لاَ يَبِيعَنَّ حَاضِرٌ لِبَادٍ ". فَقَالَ لاَ يَكُنْ لَهُ سِمْسَارًا.
Narrated Tawus: I asked Ibn `Abbas, "What is the meaning of, 'No town dweller should sell (or buy) for a desert dweller'?" Ibn `Abbas said, "It means he should not become his broker."