It was narrated from Abu Hurairah that the Messenger of Allah said: "Do not go out to meet the riders, and do not urge someone to cancel a sale he has already agreed upon os as to sell him your own goods, do not artificially inflate prices, and let not a town-dweller sell for a desert-dweller." (Sahih)
SahihSahih HadithSahih - Agreed UponBook 44 · Hadith 48