大般涅槃經義記 7.113

7.113

下次答其第二句難。答意如何？明性不斷，故得名為常、樂、我、淨。於中初言「若是斷者則應還得」反釋不斷，「若不還得則不名斷」順釋不斷。約得顯之，凡是一切可斷之法，當時雖斷，後必還得，佛性無有還得之義，明知不斷。以不斷故，如來說為常、樂、我、淨。

Next, it answers the challenge of the second clause. What is the intention of the answer? It clarifies that because the nature is unbroken, it can be called permanent, blissful, self, and pure. Therein, the initial statement, "If it were severed, it should then be regained," inversely explains that it is unbroken; "If it is not regained, then it is not called severed," directly explains that it is unbroken. Revealing it in terms of attainment: as for all dharmas that can be severed, although severed at the time, they are later necessarily regained; the buddha-nature does not have the meaning of being regained, by which one clearly knows it is unbroken. Because it is unbroken, the Tathāgata speaks of it as permanent, blissful, self, and pure.