Sell the bear's skin before one has caught the bear.

例句：

1. 1. The farmer decided to sell his farm for a profit.
   农民决定以利润出售他的农场。
2. 2. They offered their services for free in exchange for the materials.
   他们免费提供服务，作为交换材料。
3. 3. The company is selling its stock at a discount.
   该公司正在以折扣价出售其股票。