Book 4: 《里仁》 Li Ren (Brotherliness)
《里仁》 Passage 4.15
子曰：「參乎！吾道一以貫之。」曾子曰：「唯。」子出。門人問曰：「何謂也？」曾子曰：「夫子之道，忠恕而已矣。」
Legge Translation (1861)
The Master said: "Shen, my doctrine is that of an all-pervading unity."The disciple Zeng replied: "Yes."
The Master went out, and the other disciples asked, saying: "What do his words mean?"
Zeng said: "The doctrine of our master is to be true to the principles of our nature and the benevolent exercise of them to others, — this and nothing more."