Al-Lu'lu Wal-Marjan 973 — The Book of Sales (Bargains)

Ibn 'Abbas Narrated from:

Allâh’s Messenger صلى الله عليه وسلم 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.” Ibn ‘Abbâs was asked, “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.” ( Sahih Al-Bukhari, Hadith No. 367, Vol. 3)