大般涅槃經義記 7.216

7.216

下對凡夫捨受辯異，前說斷樂相同捨受，故須辯異，先舉三受，次列三名，下就辯異。「不苦不樂是亦為苦」捨異涅槃，是亦名為行苦壞苦。涅槃雖同不苦不樂，「然名大樂」涅槃異捨，「以大樂」下將義顯體，成涅槃大。

Below, distinguishing it by contrast with the neutral sensations of ordinary persons: because previously speaking of severing bliss resembled neutral sensation, it must be distinguished; it first raises the three sensations, next lists their three names, and below proceeds to analyze the distinction. "Neither suffering nor bliss is also suffering" distinguishes neutral sensation from nirvāṇa, as it is also called the suffering of conditioned existence and the suffering of deterioration. Although nirvāṇa is also neither suffering nor bliss, "yet it is called great bliss," distinguishing nirvāṇa from neutral sensation; from "by great bliss" downward uses the meaning to reveal the substance, establishing the greatness of nirvāṇa.