金口玉牙 Golden mouth and jade teeth
Explanation
金口玉牙原指皇帝的言论，比喻皇帝的命令不可更改，现比喻说话算数，言出必行。
Originally, 金口玉牙 referred to the emperor's pronouncements, meaning that the emperor's orders could not be changed. Today, it refers to someone whose word is law and whose statements are reliable.
Origin Story
话说大唐盛世，皇帝李隆基，英明神武，深受百姓爱戴。一日，他下令兴建一座宏伟的宫殿，以庆祝国家的繁荣昌盛。工匠们夜以继日地忙碌着，但进度却迟迟不见起色。李隆基得知后，龙颜大怒，下令三日内必须完工，否则严惩不贷。工匠们惶恐不安，苦苦哀求，但李隆基金口玉牙，决不更改命令。最后，工匠们加班加点，终于在期限内完成了宫殿的建造。从此，金口玉牙的故事流传至今，成为人们对君主权威的象征，也用来比喻说话算话，言出必行。
In the prosperous Tang Dynasty, Emperor Li Longji, known for his wisdom and bravery, was deeply loved by the people. One day, he ordered the construction of a magnificent palace to celebrate the nation's prosperity. The craftsmen worked day and night, but the progress was slow. Li Longji learned about it, became angry, and ordered that the palace must be completed within three days, otherwise, severe punishment would be given. The craftsmen were frightened and pleaded with him, but Li Longji remained firm in his word. Finally, the craftsmen worked overtime and completed the palace construction on time. From then on, the story of 金口玉牙 spread and became a symbol of imperial authority and at the same time a metaphor for credibility and reliability.
Usage
金口玉牙主要用于形容说话算数，言出必行的人或事。常用于褒义场合。
金口玉牙 is mainly used to describe someone or something that keeps their word and does what they say. It is often used in a positive context.
Examples
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皇帝金口玉牙，一言九鼎。
huangdi jinkouyuya yanyijiuding
The emperor's word is law.
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他的承诺如同金口玉牙，值得信赖。
tade chengnuo ruotong jinkouyuya zhide xinlai
His promise is as good as gold, trustworthy and unchangeable..