Why are officials and ministers called heavenly officials? Is there any basis or statement?

In fact, Tianguan represents the whole official department, not the minister of the official department. You can call it Tianguan, but other ministers can't.

In ancient times, there was a set of titles for six ministers, which can be traced back to the Zhou Dynasty. According to "Zhou Li", in the etiquette system of the Zhou Dynasty, the head of the hundred officials was called Zatu, and there were six officials of heaven, earth, spring, summer, autumn and winter under Zatu, who managed various affairs respectively. Later, with the evolution of history, the official system of the Zhou Dynasty was also inherited. After the establishment of the six-part system, six officials were also named after the world, spring, summer, autumn and winter. However, it should be noted that the "official" here is not an "official position", but an "official position", that is, a department, that is to say, all ministers in the official department can be called Tianguan, but Tianguan is not an official name, but the name of the whole department.

So, why use the official signature of the Zhou Dynasty? As we all know, Empress Wu Zetian changed her title to Zhou after she proclaimed herself emperor. The reason why Wu Zetian changed her country name to Zhou is also to show that she has inherited Zhou's will and is in a very positive position. Words at that time, the literati around Wu Zetian said that Zhou Pingwang's son was called, and Wu Ji's descendants were all surnamed Wu. Because Wu Zetian was also surnamed Wu, she thought she was a descendant of Zhou Tianzi, and changed her title to Zhou after she proclaimed herself emperor. Since Wu Zetian thought that she was adhering to the will of the Emperor of Zhou, it was natural for her to abide by the Rites of Zhou and change the name of the six departments with the Rites of Zhou. In this case, the officials of Wu Zetian's reign were also called Tianguan. In fact, apart from the six departments reorganized in Zhou Li, some other official positions have also been reorganized, so I won't go into details here.

After the fall of Wu Zetian, although Li Tang was restored, many political systems were still inherited from Wu Zetian's period, so six decrees were also preserved, and the official minister was still called Tianguan.

In a word, officials and ministers are called heavenly officials, which can be traced back to the Zhou Dynasty at the earliest.