大般涅槃經集解 14.18

14.18

案僧宗曰：水酒瓶者，為不空空譬也。乃可無水而器不空，明涅槃乃空無生死耳，而常果不空也。

Sengzong states: The flask for water or wine is a metaphor for 'not empty of emptiness'. There may be no water, yet the vessel is not empty; this clarifies that nirvāṇa is merely empty of birth-and-death, whereas the eternal fruit is not empty.