Liu Xiang of the Han Dynasty told such a story in "Talking about Yuan Jianben": Duke Jinping of the State of Jin asked Shi Kuang, "I am seventy years old, and I am afraid I will die and learn." Shi Kuang said, "Why not light a candle?" Gong Ping said, "An is a minister. Are you kidding me?" Shi Kuang said, "Do blind ministers dare to play with their princes? I heard it: less and more eager to learn, like the sunrise sun; Strong and eager to learn, such as the light of Japan and China; Old and studious, bright as a candle. What is the light of the candle? " Gong Ping said, "Good!"

Teenagers are eager to learn, such as the rising sun, shining brightly; Mature and eager to learn, like the midday sun, bright and gorgeous; Learning in old age, like burning candles, will also release a ray of light. Which is better than groping in the dark?

Yan Zhitui in the Northern Song Dynasty also paid great attention to encouraging future generations to study hard in their later years. He quoted Shi Kuang's metaphor in Family Instructions of Yan Family: It's too late to be married (20 years old) in the world. Young scholars, such as the light of sunrise, old scholars, such as the night walk by candlelight, are still virtuous.

In Yan Zhitui's "Mianxue Chapter of Yan Family Instructions", there is also a saying that "young scholars, such as the light of the morning glow, old scholars, like holding a candle at night".