What is the significance of the ayah in surah Ali Imraan (3.77) that was revealed in response to a man who cheated another Muslim by swearing to a false price for his merchandise?
 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)