Source: Shi Shuo Xin Yu by Liu Yiqing and others in Southern Dynasties.
Original text:
Kong Rong was shut down, and both China and foreign countries were afraid. When Rong's son was nine years old, the youngest was only eight. His son was embarrassed by the nail. Let's talk about the emissary: "Ji's crime ends with his body, and his son can get nothing." My son Xu Jin said, "My Lord, have you seen any finished eggs under the covered nest?" I found them.
Translation:
Kong Rong was arrested, and both inside and outside the court were very frightened. At that time, Kong Rong's two sons were nine and eight. The two sons are still playing with nail cutting, and they are not afraid at all.
Kong Rong said to the messenger, "The blame can be limited to yourself. Can two sons save their lives? " His son said calmly, "Did Dad ever see a complete bird's egg under the overturned nest?" Soon, the police who arrested them arrived.
The story background described in this article is that when Cao Cao was preparing to March south to Liu Bei and Sun Quan, Kong Rong advised Cao Cao not to go south. Cao Cao didn't listen to him, and Kong Rong made a few grumbles behind his back, which just reached the ears of the ancient empire who had always been at odds with him.
So they added fuel to tell Cao Cao that Cao Cao was furious and ordered the Kong Rong family to be executed. And his sons were still young, just a few years old. Children know that officials will not let them go. They said to Kong Rong unhurriedly, "Have you ever seen a bird's egg still intact under an overturned nest?"
It shows their unyielding integrity, which makes people feel that Kong Rong's two children are young, but they have inherited their father's tolerance and wisdom. This is the origin of the idiom "There are no eggs left under the nest".