大般涅槃經義記 4.102

4.102

自下第二辯明如來得大涅槃，不捨世間，常共無常、樂共苦等。於中有四：一我共無我、二「佛法猶如鴛鴦共」下明樂共苦、三「異法我」下重復明其我共無我、四「同諸煩惱所造有」下明常共無常。

From here below is the second [part], which explains that the Tathāgata attains Great Nirvāṇa without abandoning the world, permanence being together with impermanence, bliss being together with suffering, and so forth. Therein are four [topics]: 1. self being together with non-self; 2. from "The Buddha's teachings are like mandarin ducks together" onward, clarifying bliss being together with suffering; 3. from "Different dharmas, self" onward, clarifying once again self being together with non-self; 4. from "Identical to existence created by all afflictions" onward, clarifying permanence being together with impermanence.