Sahih Bukhari Volume 6, Book 60, Hadith Number 73.

Narrated By ‘Abdullah bin Abu Aufa : A man displayed some merchandise in the market and took an oath that he had been offered a certain price for it while in fact he had not, in order to cheat a man from the Muslims. So then was revealed: “Verily! Those who purchase a small gain at the cost of Allah’s Covenant and their oaths…”(3.77)