The Book of Transactions (Kitab Al-Buyu`)

Muslim :: Book 10 : Hadith 3663

Abdullah b. Dinar narrated that he heard Ibn 'Umar (Allah be pleased with them) saying: A man mentioned to the Messenger of Allah (may peace be upon him) that he was deceived in a business transaction, whereupon Allah's Messenger (may peace be upon him) said: When you enter into a transaction, say: There should be no attempt to deceive.