肇論新疏 3.8

3.8

涅槃之道，蓋是三乘之所歸、方等之淵府，渺漭希夷，絕視聽之域；幽致（旨）虛玄，殆非群情之所測。

The Dao of nirvāṇa is indeed that to which the three vehicles return, the deep reservoir of the vaipulya [teachings], vast, indistinct, subtle, and silent, cutting off the realm of seeing and hearing; its profound purport is empty and abstruse, scarcely something that the sentiments of the multitude can measure.