Prophetic Commentary on the Qur'an (Tafseer of the Prophet (pbuh))
Bukhari :: Book 6 :: Volume 60 :: Hadith 73
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)