“About the case of a man who buys food, every kur (a certain amount) for a certain price, then prices rise or fall when he has measured only a certain part, and the owner of food refuses to deliver to him the rest, abu ‘Abd Allah (a.s.), has said, ‘If on the day of purchase he has priced the food and that the food is his, then the remaining food is also his; but if he had only bought without any condition then only what he has paid for is his.’”