闻其歌知是鸟，听其言知是人。

A bird may be known by its song.

youdao

要了解人们真正在想什么，就得观其行，而非听其言。

To know what people really think, pay regard to what they do, rather than what they say.

youdao

常言道，看一个人是否真诚，不能只听其言，更要观其行。

As the saying goes, "To judge a person whether he is honest or not, you'd better observe his conduct rather than his words."

youdao