大般涅槃經集解 18.67

18.67

案僧亮曰：空性是常，見常故常也；不見常者，是無常也。僧宗曰：應言常上作無常想，名不修空也。生死是空、佛果不空，若說佛果為空者，則失分齊，乖修空之道也。壽命短促者，所執既乖，不得妙常，豈非短促耶？

Sengliang says: "The nature of emptiness is permanent; because one sees the permanent, it is permanent; one who does not see the permanent is impermanent." Sengzong says: "It should be said that forming the conception of impermanence regarding the permanent is called not cultivating emptiness. Saṃsāra is empty; the fruit of buddhahood is not empty. If one says that the fruit of buddhahood is empty, one loses the correct bounds and goes against the path of cultivating emptiness. As for 'lifespan is short and fleeting': since what is held to is contrary [to truth], one does not attain wondrous permanence; how could it not be short and fleeting?"