大般涅槃經義記 7.177

7.177

次四如中，初一明其牽人作惡，為四大身多作罪故；第二明其獨能為害；第三明其性相乖反；第四明其難可親近。

Among the next four that are 'like [snakes]': the first clarifies that they drag people into committing evil, because for the sake of the body of the four elements one creates many transgressions; the second clarifies that they alone can do harm; the third clarifies that their natures and characteristics are mutually conflicting; the fourth clarifies that they are difficult to approach.