"promise": sincerity. "Persistence": observation. "Jue": it. "Middle": Zhongzheng. ?
This idiom comes from Dayu Mo. Shun warned Yu here: people's hearts are in danger, and the Tao is difficult to understand. Only by earnestly and sincerely grasping the right path can we govern the country well. Interpretation means that words and deeds are impartial and in line with the right path.
Extended data:
Dayu Mo is from Shangshu, one of the five Confucian classics, and records the ancient historical materials of Dayu, Boyi and Shun's political planning. Dayu is a courtier of Shun. He made great contributions to flood control, and later he was called Dayu. Mo, Mou. The first paragraph of this paper describes the political plans of Dayu, Boyi and Shun, so it is called Dayu Mo. This is one of Mei's fake books.
References:
Allow yourself to be dumbfounded-Baidu Encyclopedia