《论衡·卷十一·答佞篇》
大圣人难于识别大佞人，大佞人不怕大圣人，怎么能说容易识别呢？
大圣难知大佞，大佞不忧大圣。
It is difficult for a great sage to recognize a great villain, and a great villain is not afraid of a great sage. How can it be said that it is easy to recognize?