Keeping Promises
Honoring one's word as a matter of righteousness.
Trustworthiness (xin) is connected to yi. Keeping promises, being reliable, and meaning what one says are all expressions of righteousness. One's word should be one's bond.
If a person lacks trustworthiness, I don't know what they are good for.
Trustworthiness is essential for social functioning.
Analects
Written about in
- What Confucianism says about what to say and what to leave unsaid
Trustworthiness, xin, is what makes speech cost something. Confucius says he does not know what a person lacking it is good for, which is close to the harshest thing the Analects says about talk.