During the Spring and Autumn period, Confucius led his disciples on a tour of various states. After fleeing from the State of Chen to the State of Cai, he was not highly regarded by the ruler of Cai. He often sighed, feeling that he was "eating all day without applying his mind."

One day, he found his disciple Zai Yu sleeping soundly at noon. Infuriated, Confucius declared that Zai Yu was "rotten wood that cannot be carved."

His other disciples quickly came to console him. Confucius then said, "From now on, I will listen to what they say and observe what they do. Let each of them act accordingly." This marked a shift in his approach to judging his students.