1. As the/an saying goes 俗话说.
2. As an old saying goes古人云.；有一句老话说.
用法如下：
1. As the/an saying goes that where there is a will,there is a way.
俗话说有志者事竟成.
2. As an old saying goes," opportunity is for the ready man".
俗话说“机遇总是给有准备的人”,“有备而战,战无不胜”.