Mukhtasar Bukhari

Narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that a man said to the Prophet (peace and blessings of Allah be upon him) that he often suffered loss in buying and selling. The Prophet (peace and blessings of Allah be upon him) said: "When you buy and sell, say: (i.e., in buying and selling) there should be no deception or loss."