大般涅槃經集解 10.73

10.73

案僧亮曰：釋上句也。湛然故無盡也。僧宗曰：移劫不窮，故言無盡；即是不盡，故離一切盡也。

Sengliang states: This explains the preceding phrase. Because it is serene and pure, it is without exhaustion. Sengzong states: Over countless eons it is never depleted, hence it is said to be 'without exhaustion'; this is being 'unexhausted', and thus it is 'free from all exhaustion'.