In 520 BC, King Jing of Zhou passed away. According to royal tradition, his legitimate heir, Prince Ji Meng, should have succeeded the throne. However, the king had intended to make his eldest son, Ji Zhao, who was born of a concubine, the crown prince. He had discussed this plan with the Grand Master Bin Meng but died before he could carry it out.
After King Jing of Zhou died, the nobles Shan and Liu conspired to eliminate Bin Meng and install Ji Meng as the new ruler. Ji Meng ascended the throne, becoming known as King Dao of Zhou. However, the court officials Yin Wengong, Gan Pinggong, and Zhao Zhuanggong refused to accept this outcome and resolved to install Prince Chao instead. They joined forces and launched an attack on the Liu clan.
Defeated, the Liu clan fled in disgrace to the state of Jin
Soon after, King Dao of Zhou died of illness, and the clans of Shan and Liu installed his full younger brother Gai as ruler, historically known as King Jing of Zhou. However, Prince Chao continued his rebellion and, with the support of Yin Wengong and others, declared himself king. The people of Jin called Gai the "Eastern King" and Chao the "Western King." The two factions waged civil war for years, neither able to unify the realm.
In 517 BCE, Duke Qing of Jin summoned the feudal lords to a covenant at Heirang (northwest of present-day Qinshui, Shanxi) to discuss stabilizing the Zhou royal house. Among those attending were Zhao Yang of Jin, Shu Yi of Lu, Yue Daxin of Song, Beigong Xi of Wei, and You Ji of Zheng.
At the meeting, Zhao Yang asked You Ji about "ritual propriety." You Ji replied, "Our high minister Zichan once said that ritual propriety is the warp of heaven—the norm of the Way of Heaven—and also the righteousness of earth—the standard of the land. All people must take this as the basis for their actions; it cannot be altered, much less doubted."
Zhao Yang thanked his teacher, vowing to remember the lesson for life, and the other representatives from various states present couldn't help but look on with deep respect.
Zhao Yang then proposed that all states should follow ritual propriety by providing King Jing of Zhou with troops and supplies to help him return to the capital. However, Yue Daxin of Song disagreed, arguing, "Song is a descendant of the Shang dynasty, and the Zhou court has always treated us as honored guests. A guest has no obligation to send armies and grain to the host."
A Jin official named Mi Mou, who was accompanying Zhao Yang to the meeting, immediately countered Yue Daxin's argument, pointing out that the State of Song had always followed the alliance leader's arrangements in the past, yet now, when efforts were needed to restore the Zhou royal house, they raised such objections—this was a display of discourtesy.
Yue Daxin was left speechless, forced to accept the official order and withdraw
Later, people used the idiom "Heaven's Law and Earth's Way" to describe something that is perfectly justified, unalterable, and beyond doubt.
Source: *Zuo Zhuan*, "Duke Zhao's Twenty-Fifth Year"
Meaning of the Idiom: Later, the Chinese idiom "天经地义" came to describe how something is perfectly justified, unalterable, and beyond doubt.