Sunan Ibn Majah, Chapter: The Chapters on Business Transactions

"I came to the Messenger of Allah (saw), during one of his 'Umrah at Marwah and said: 'O Messenger of Allah, I am a woman who buys and sells. When I want to buy something, I state a price less than I want to pay, then I raise it gradually until it reaches the price I want to pay. And when I want to sell something, I state a price more than I want, then I lower it until it reaches the price I want.' The Messenger of Allah (saw) said: 'Do not do that, O Qailah. When you want to buy something, state the price you want, whether it is given or not. And when you want to sell something, state the price you want, whether it is given or not.'"