In the Book of the Later Han, Wang Ba is told: “Of those from Yingchuan who followed me, all have gone. You alone stayed. Strive on! A strong wind shows which grass is tough.” The last words, jifeng zhi jingcao (疾风知劲草), became an idiom. Another Han history, the Dongguan Hanji, names the emperor as the speaker.
The New Book of Tang records a poem given to the minister Xiao Yu: “A strong wind shows which grass is tough. Times of turmoil show which minister is sincere.” The Handian dictionary explains the idiom this way: only a severe test shows who is truly strong.