Xiǔ mù nán diāo
Translation: Rotten wood cannot be carved.
Meaning: Something that is already bad cannot be made better, or prettier. You cannot change the true nature of such things. An English equivalent would be: “You can’t teach an old dog new tricks.”
Confucius had a student named Zai Yu, who had a way with words. At first Confucius thought that he could be a very promising student. Before long, however, Zai Yu revealed….