There is a famous saying about keeping your promise: don't forget your promise anyway.

Keeping a promise is like defending your honor. -Balzac

A word spoken is past recalling. -China proverb

Treat people with sincerity, and people will not bully me; Nothing can be done by being honest about things.

—— (Middle) Feng Yuxiang

Credit is both an intangible force and an intangible wealth.

-(Japanese) Kōnosuke Matsushita

Conscience is the sentry in each of us. It stands guard there, watching us not do anything illegal. -(UK) Mao Mu

A word spoken is past recalling. -China proverb

If you live honestly, you must have a clear conscience.

-(Su) Gorky