大般涅槃經義記 2.37

2.37

下次辯義，常樂我淨理實遍通一切佛法，然今隱顯，我偏就人，餘三就法。「我是佛」者，自在名我，自在之用在於佛人，故說為我。又復我者，人之別稱，故就佛人而說其我。「常法身」者，法身佛體，顯本法成，性出自古，體無變異，明常義顯，故說為常。「樂涅槃」者，涅槃是滅，滅離眾苦，寂樂義顯，故說為樂。「淨是法」者，謂三寶中法寶之體，能治垢染，故說為淨。

Next is discerning the meaning: permanence, bliss, self, and purity in principle truly pervade all buddhadharmas; yet now, distinguishing what is hidden and revealed, 'self' is treated specifically in terms of the person, while the other three are treated in terms of dharmas. 'The self is the Buddha': sovereignty is called 'self'; since the function of sovereignty resides in the Buddha-person, it is spoken of as 'self.' Furthermore, 'self' is a distinct name for a person; hence, it is spoken of as 'self' with respect to the Buddha-person. 'Permanence is the dharmakāya': the dharmakāya is the Buddha's substance, which is realized through the revelation of the fundamental Dharma; its nature originated from antiquity, and its substance is free from change; because the meaning of permanence is distinctly demonstrated, it is spoken of as 'permanent.' 'Bliss is nirvāṇa': nirvāṇa is cessation, which is the cessation of and departure from all suffering; because the meaning of serene bliss is distinctly demonstrated, it is spoken of as 'bliss.' 'Purity is the Dharma': this refers to the substance of the Dharma jewel among the Three Jewels, which is able to remedy defilement; hence it is spoken of as 'pure.'