It is narrated from Hazrat Ibn Abbas (may Allah be pleased with them both) that the Noble Prophet (peace and blessings be upon him) said: Do not go out of the city to meet a caravan of traders in order to buy their goods at a low price and then sell them at a higher price, and do not collect milk in the udders of a she-camel to sell her, and do not artificially raise the price of goods for one another.