a common saying的用法和样例：
- It is a common saying which we often hear in the mouths of the vulgar.
- A common saying goes,"Business is as fierce as war".
- It is a common saying that we do not value a thing till we lose it.
- There is a common saying in China that practice is the sole criterion for testing truth.
- A common saying goes,"Knit the brows and you will hit upon a stratagem." In other words,much thinking yields wisdom.