Sahih Bukhari, Chapter: Witnesses

A man displayed some goods in the market and took a false oath that he had been offered so much for them though he was not offered that amount Then the following Divine Verse was revealed: "Verily! Those who purchase a little gain at the cost of Allah's covenant and their oaths . . . Will get painful punishment." (3.77) Ibn Abu Aufa added, "Such person as described above is a treacherous Riba-eater (i.e. eater of usury).