The text of the sutra is divided into three sections. The first portion is the introduction. The second portion is the main body of the text that gives the correct guiding principles. The third portion is the history of the transmission of the text. These three parts are called the excellent opening, the excellent middle, and the excellent ending.
The introduction is like the head, complete with eyes, ears, and nose. The main body of the text is like the body, complete with all the internal organs. The transmission history is like the hands and feet, which move unimpeded.
In sum, the introduction covers the overall structure of the sutra, while the transmission history shows that the bestowal of the teaching has been unimpeded. The connection of these two portions with the main body of the sutra is not a minor matter. Lately people have not understood this. When they read the sutras, they delve a bit into its principles, then plunge into the main body of the text, treating the introduction and the transmission history as if they were empty formulas. If this were true, why are we told that both the opening words and the closing words of a sutra are also excellent?