Sima Niu asked about goodness. Confucius said: “A person who practices goodness is cautious in speech.” Sima Niu said: “Cautious in speech? Is that what you call goodness?” Confucius said: “When something is difficult to do, how is it possible not to be cautious in speaking about it?”
Confucius replies to the third successive question on goodness with a pun: the characters 仁 (rén/goodness) and 訒 (rèn/speak cautiously) are homonyms, though spoken in different tones.
No doubt he is making a veiled criticism of Sima Niu’s loquaciousness with his veiled comment. I wonder if Sima Niu took the hint.
Sima Niu was a disciple of Confucius. He may or may not have been the brother of Huan Tui (桓魋), an official of the state of Song who tried to have Confucius murdered in Book 7, Chapter XXII of the Analects.