大般涅槃經義記 3.179

3.179

二「何以」下釋不了義。言「何以故」，徵前起後，一切燒等何故不了？不能解了如是義故對以釋之，依止生心不能解向燒等諸義，局在有為，故名不了。

Second, from "Why?" onwards explains non-definitive meaning. The statement "Why?" queries what precedes to introduce what follows: why is "all is burned" and the like non-definitive? "Because of not being able to understand such meaning" is offered in explanation: when relying [on teachings], generating thoughts while failing to understand the aforementioned meanings of burning and so forth, restricting them to the conditioned—this is why it is named non-definitive.