The meaning of this sentence is: at the age of 30, I learned etiquette and behaved appropriately; At the age of forty, you can become a knowledgeable person without confusion; When I was fifty years old, I learned the basic laws of astrophysics.

Source: Confucius, The Analects of Confucius, Chapter 2, Politics.

Original text:

Confucius said: "I have five out of ten, but I am determined to learn. I stand at thirty, I am not confused at forty, I know my destiny at fifty, I listen at sixty, I follow my heart at seventy, and I don't overstep my bounds."

Explanation:

Confucius said: "I became interested in learning when I was fifteen." At the age of thirty, I can do things independently. At the age of forty, I don't have to be confused. At the age of fifty, I learned what human resources can't control. Sixty years old, I can listen to different opinions. Only when I am seventy years old can I do whatever I want without overstepping the bounds. "

Confucius (September 28th BC1year-April BC1year), surnamed Kong, was born in the late Spring and Autumn Period (now Qufu, Shandong) and his ancestral home was Li Yi (now Xiayi, Henan), an ancient thinker and educator in China.

Confucius initiated the wind of private schools and advocated benevolence, righteousness, courtesy, wisdom and faith. There are 3,000 disciples, including 72 sages. He led some disciples to travel around the world for thirteen years, and revised the six classics of Poetry, Book, Rite, Yue, Yijing and Chunqiu in his later years. Confucius was one of the most learned scholars in the society at that time. After his death, his disciples recorded the words and deeds, quotations and thoughts of Confucius and his disciples and compiled The Analects.

This book is regarded as a Confucian classic. Confucius was honored as a "saint of heaven" and a "muduo of heaven" when he was alive, and even as a saint, the most holy, the most holy teacher, the most holy teacher, the king's teacher and the eternal teacher of Confucius by later rulers. His thoughts have a far-reaching influence on China and the world, and he is listed as the first of the "Top Ten Cultural Celebrities in the World".

With the expansion of Confucius' influence, "Confucius Sacrifice Ceremony" once became a "big sacrifice" at the same level as China's ancestor worship.

Source: Baidu Encyclopedia webpage link