淨名經集解關中疏 2.257

2.257

淨解菩薩曰。有為無為為二。若離一切數則心如虛空。以清淨惠無所礙者。是為入不二法門　四相有為也。四相滅無為也。相本不起。今則無滅無二也。叡曰。數即有為無為也。

The Bodhisattva Śuddhadhimukti said, "The conditioned and the unconditioned constitute duality. If one is free from all classifications (reckonings), the mind is like empty space; when with pure wisdom one encounters no obstruction, this is entering the dharma gate of non-duality."
The four characteristics are conditioned; the extinction of the four characteristics is unconditioned. The characteristics fundamentally do not arise, and now they do not perish; this is non-duality. Sengrui says, "Classifications (reckonings) refer precisely to the conditioned and the unconditioned."