維摩經玄疏 6.55

6.55

三、明有空門者，即三藏教明正因緣生滅之有空，若稟此教，能破偏執有無之惑，見因緣有空，發真無漏。因有空見真，有空即第一義之門也。此是迦旃延因入道故，作《昆勒論》還申此門也。

Third, clarifying the gate of existence and emptiness: this is the Tripiṭaka teaching clarifying the existence and emptiness of the arising and perishing of correct causes and conditions. If one receives this teaching, one can destroy the delusions of biasedly grasping existence or non-existence, see the existence and emptiness of causes and conditions, and generate true taintlessness. Because of existence and emptiness one sees the truth; existence and emptiness is the gate to the supreme meaning. This is what Kātyāyana, because he entered the path thereby, composed the Peṭakopadesa to further set forth as this gate.