大般涅槃經義記 2.188

2.188

In the first section there are three dialogues. First, clinging to the previous [teaching on] the non-existence of the exhaustion of conditioned phenomena, he challenges the Buddha with impermanence; below, the Buddha answers him that the causes and effects of birth and death are impermanent dharmas, and because the Tathāgata has severed them completely, he is called permanent. Second, Kāśyapa pursues the words to challenge him again: like that flashing iron, when its heat and red color have ceased they no longer exist; the Tathāgata is also like this—having ceased, he no longer exists; what can be called permanent? Below, the Buddha answers him: the afflictions that have been severed will never arise again, and therefore he can be called permanent. Third, Kāśyapa challenges and undermines the Tathāgata's meaning of not arising again: like iron, once cooled, if placed back into fire, the red color arises again; if the Tathāgata is like this, after afflictions have ceased, fetters should arise again, and he could not be permanent. Below, the Buddha shifts the simile to explain and establish non-arising, revealing that there is the meaning of permanence: like burning wood, having ceased, there are ashes and it never becomes wood again; the Tathāgata is also like this—after afflictions have ceased, the dharmakāya permanently endures and never produces fetters again, and therefore he can be permanent.