The meaning of this sentence is: at the age of thirty, you understand the etiquette, and your words and deeds are all appropriate; at the age of forty, you can become a knower, without confusion; at the age of fifty, you understand the fundamental laws of heavenly physics.

Source: "The Analects of Confucius·Chapter 2·Wei Zheng Chapter" by Confucius

Original text:

Confucius said: "I have five out of ten, and I am determined to learn. , stand firm at thirty, have no doubts at forty, understand the destiny at fifty, be attuned to your ears at sixty, follow your heart's desires at seventy, and do not exceed the rules."

Explanation:

Confucius said: "I started to be interested in learning when I was fifteen. I was able to do things independently when I was thirty. I was not confused when I was forty. I knew what things cannot be controlled by human beings when I was fifty. I was able to listen when I was sixty. When you are seventy years old, you can do whatever you want and not go beyond the rules."

Confucius (September 28, 551 BC - April 11, 479 BC), surnamed Zi. , Kong family, named Qiu and styled Zhongni, was a native of Zou Yi (now Qufu, Shandong Province) of the state of Lu in the late Spring and Autumn Period, and his ancestral home was Li Yi (now Xiayi, Henan Province) of the Song state. He was an ancient Chinese thinker, educator, and founder of the Confucian school.

Confucius created the style of private lectures and advocated benevolence, justice, etiquette, wisdom and trust. He had three thousand disciples, among whom were seventy-two sages. He led some of his disciples to travel around the world for thirteen years, and in his later years he revised the Six Classics of Poems, Book, Rites, Music, Yi, and Spring and Autumn. Confucius was one of the most erudite scholars in society at that time. After his death, his disciples and his subsequent disciples recorded the words, deeds, quotes and thoughts of Confucius and his disciples, and compiled them into The Analects of Confucius.

This book is regarded as a Confucian classic. Confucius was revered as the "Sage of Heaven" and "The Wooden Duo of Heaven" when he was still alive. He was also honored by later generations of rulers as the Saint of Confucius, the Most Holy, the Most Holy Teacher, the Great Saint Wenxuan King's Teacher, and the Teacher of All Times. His thoughts have had a profound impact on China and the world, and he is listed as the first among the "Top Ten Cultural Celebrities in the World".

With the expansion of Confucius' influence, the "Confucius Ceremony" to worship Confucius once became a "big sacrifice" on the same level as the Chinese ancestor gods.

Data source: Baidu Encyclopedia web link