Kong Li, also known as Boyu, was the biological son of Confucius.
Some of Confucius's disciples once suspected that he held back in his teaching, not necessarily passing on all his knowledge to his students. Others wondered if he taught his own son more and better.
One day, Confucius's disciple Chen Kang quietly asked Boyu, "Have you heard any special teachings from the Master?"
Boyu replied, "No, but once my father stood alone in the courtyard, and when I passed by, he asked, 'Have you studied the Book of Songs?' I said, 'No.' He said, 'Without the Songs, your speech will lack liveliness.' So I went and studied them. Another time, I met him in the courtyard, and he asked, 'Have you studied the Book of Rites?' I said, 'No.' He added, 'Without the Rites, you won't know how to handle people and affairs.' So I studied that too. Those were the only two things he taught me privately."
Chen Kang was very satisfied with Kong Li's reply and said, "I asked just one question and gained three insights: I learned the value of studying the Book of Songs, understood the importance of studying the Book of Rites, and realized more clearly that a gentleman does not show special favoritism toward his own son."
Later generations adopted "Ask One, Gain Three" as an idiom, meaning to ask little but receive much in return.
Source: *The Analects*, Chapter "Ji Shi"
Meaning of the Idiom: Later, the Chinese idiom "问一得三" came to describe how to ask little but receive much in return.