Language:
كتاب البيوع
34  
Sales and Trade
(71)
Chapter: It is forbidden to meet the caravans on the way (to buy the goods away from the market)
(71)
باب النَّهْىِ عَنْ تَلَقِّي الرُّكْبَان
Sahih al-Bukhari 2163

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."

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.‏
Reference : Sahih al-Bukhari 2163
In-book reference : Book 34, Hadith 114
USC-MSA web (English) reference : Vol. 3, Book 34, Hadith 372
  (deprecated numbering scheme)