yán bì xìn, xíng bì guǒ 言必信，行必果
Promises Must Be Kept; Actions Must Be Resolute.
The expression comes from Mozi and The Analects. Followers of Mozi and Confucian ethics admired those who could keep their promises and whose actions were resolute. They believed speech and action should match. However, Confucius (551-479BC) and Mencius (372?-289BC) took this further to apply to rulers who, only by being as good as their words and trustworthy in their speech, could earn the confidence and support of their subjects who, in turn, would be truthful with them. For Confucius, this principle, rather than be followed too rigidly, should in practice be applied on the basis of what is ethical under specific conditions and after careful weighing the pros and cons. Later, the expression came to refer to honest speech and firm action, keeping one’s word, and also “suit action to word.”
Promises must be kept; actions must be resolute. They should fit together like the two parts of a tally stick: everything said must be put into practice. (Mozi)
Always keeping one’s word without forethought is the sign of an obstinate and stubborn person, but he can still be considered a gentleman of a second degree. (The Analects)
For a person of exceptional virtue, not every word has to be credible nor every action firm as long as standards of righteousness are followed. (Mencius)