The Great Learning, Commentary of the Philosopher Tsang, Chapter 4. The above fourth chapter of commentary explains the root and the issue.
The Master said, "In hearing litigations, I am like any other body. What is necessary to cause the people to have no litigations?" So, those who are devoid of principle find it impossible to carry out their speeches, and a great awe would be struck into men's minds; ‹ this is called knowing the root.
<€CH> The above fourth chapter of commentary explains the root and the issue.
Text source: The Great Learning. Translated by James Legge.