大般涅槃經義記 9.222

9.222

喻中有二：一約血乳生出血乳，明不善陰生善五陰。「是故我先說生佛性如雜血乳」辨法同喻，是從不善生善陰故。佛於此經先明三乘，同性之中說生佛性。「如雜血」者已下，約喻顯法。「血者即是無明行等」約喻以顯不善五陰，「乳即善陰」約喻以顯善五陰也。

In the similes there are two parts: first, based on blood and milk producing blood-tinged milk, it clarifies that unwholesome aggregates give rise to the wholesome five aggregates. "Therefore, I previously spoke of the produced buddha-nature being like milk mixed with blood" distinguishes the dharma corresponding to the simile, because the wholesome aggregates are produced from the unwholesome. The Buddha in this sūtra first clarified the three vehicles, and in the context of their shared nature spoke of the produced buddha-nature. From "like mixed blood" downward, it illuminates the dharma by means of the simile. "Blood is precisely ignorance, conditioned formations, and so forth" illuminates the unwholesome five aggregates by means of the simile; "milk is the wholesome aggregates" illuminates the wholesome five aggregates by means of the simile.