君子一言，驷马难追

lit. once said, a team of horses cannot unsay it (idiom); a promise must be kept

a promise worth one thousand in gold (idiom); a promise that must be kept

a promise worth one thousand in gold (idiom); a promise that must be kept

one must be a man of his word and resolute in his work (proverb)

each word carries weight; a promise must be kept (idiom)

to speak and keep one's promise (idiom); as good as one's word