Narrated ‘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)
Sahih Bukhari, Volume 6, Book60, Number 73