大般涅槃經義記 2.40

2.40

In the second section, "I shall now explain the three superior cultivations": below, the four cultivations of permanence, bliss, self, and purity are explained; it is only because they now directly counter the previous three false cultivations that it says "three." Stating that he will himself explain the dharmas of the three superior cultivations reveals that what the bhikṣus cultivate is unreal.