淨名經集解關中疏 2.258

2.258

那羅延菩薩曰。世間出世間為二。世間性空即是出世間。於其中不入不出不溢不散。是為入不二法門　什曰。世間三界也。出世間解脫也。悟世性定無入無出故不二也。

The Bodhisattva Nārāyaṇa said, "The mundane and the supramundane constitute duality. The nature of the mundane being empty is itself the supramundane. Within it, there is no entering and no exiting, no overflowing and no dispersing. This is entering the dharma gate of non-duality."
Kumārajīva says, "The mundane refers to the three realms; the supramundane refers to liberation. Realizing that the nature of the mundane is fixedly devoid of entering or exiting is non-duality."