大般涅槃經義記 7.224

7.224

第三門中，身淨列名，次辯其相，「身若無常」舉穢顯淨，「如來常」下彰淨異穢，「以大淨」下將義顯體，成涅槃大。

In the third section, purity of body is listed by name, and next its characteristics are discriminated. "If the body is impermanent..." adduces defilement to reveal purity. From "The Tathāgata is eternal..." onward, it displays that purity is distinct from defilement. From "Because of great purity..." onward, meaning is taken up to reveal the essence, establishing the greatness of nirvāṇa.