Yang Zhu had a younger brother named Yang Bu.
One day, Yang Bu went out wearing white clothes. It happened to rain, so he took off his white clothes, changed into black ones, and returned home. His dog did not recognize him in the different clothes and came at him, barking fiercely.
Yang Bu grew angry and was about to beat the dog. At that moment, Yang Zhu said to him, "Do not beat it. You might make the same kind of mistake. If your dog went out white and came back black, wouldn't you be surprised?"