Tao Te Ching

“The skilled reader turns it over and over in his mind, and once he gets it, draws on it his whole life, finding that it has no limits.”

— Zisi 子思 481 – 402 BCE via Daniel K. Gardner
(Kong Ji or Tzu-Ssu)
Confucius' grandson and early influence on Neo-Confucianism
from Doctrine of the Mean, Maintaining Perfect Balance, Zhongyong 中庸