Sahih Al Bukhari (666)

`Abdullah ibn Abu Awfa narrated: 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).