大般涅槃經義記 6.354

6.354

問曰：殺淺，涅槃義深，云何以深而況淺乎？釋言：是中以易況難，就涅槃法明非有無，理在易知。就殺辨之，相在難識，故今舉彼易知涅槃以況殺矣。喻中，「涅槃非有非無」明涅槃體，於迷非有，於解非無，「而亦是有」是有圓也。

Question: Killing is shallow, while the meaning of nirvāṇa is profound; why illustrate the shallow by means of the profound? Explanation: Here, the difficult is illustrated by means of the easy. In terms of the dharma of nirvāṇa, explaining that it is neither existent nor non-existent is an easy principle to understand. Discerning it in terms of killing, its characteristics are difficult to recognize; therefore, he now raises that easily understood nirvāṇa to illustrate killing. Within the analogy, "Nirvāṇa is neither existent nor non-existent" clarifies the substance of nirvāṇa: to the deluded it is not existent, and to the awakened it is not non-existent. "And yet it also is existent" refers to the completeness of its existence.