Volume 3, Book 34, Number 367:
Narrated Tawus:
Ibn ‘Abbas said, “Allah’s Apostle said, ‘Do not go to meet the caravans on the way (for buying their
goods without letting them know the market price); a town dweller should not sell the goods of a
desert dweller on behalf of the latter.’ I asked Ibn ‘Abbas, ‘What does he mean by not selling the
goods of a desert dweller by a town dweller?’ He said, ‘He should not become his broker.’ “