菩薩戒義疏 2.18

2.18

Third, the precept against eating meat: it severs the mind of great compassion. For a mahāsattva, cherishing compassion is primary, so all [meat] is completely cut off. In the gradual teachings of the śrāvakas, the three kinds of pure meat and so forth were initially permitted, but later these too were entirely severed. The text says: "You should know that the present meaning is to sever meat." The "Four Marks Chapter" of the Mahāparinirvāṇa-sūtra explains the three kinds, nine kinds, and ten kinds in detail. The narration of matters has three stages: first, explaining the faults; second, prescribing what is not proper; third, adducing the wrongdoing and concluding the offense. If there is a severe illness and taking it as medicine can cure it, according to the Vinaya it may be eaten, or perhaps it should not be prohibited.