大般涅槃經集解 56.16

56.16

案僧亮曰：若無而能生者，角亦無酪，獨何從乳而不從角耶？寶亮曰：同是無酪，角亦應有，而角不生，但乳能生，說知先有也。

Sengliang comments: If what is absent can produce it, the horn also lacks curd; why does it come solely from milk and not from the horn? Baoliang comments: Being equally without curd, the horn should also have it; yet the horn does not produce it, while only milk can produce it, so we know it existed previously.