大般涅槃經集解 2.31

2.31

案僧亮曰：眾生厭苦。苦從惑起，滅苦要先斷惑。惑有輕重，重名為見、輕者曰疑。疑尚須斷，況復見耶？斷疑唯佛，可不問乎？僧宗曰：自此之前唯說無常；今明常理，教與昔反，事則應疑。雖復言不指的，而意在於此也。寶亮曰：此是如來最後宗極之教，故勸令問。

Sengliang states: Living beings loathe suffering. Suffering arises from delusion; to extinguish suffering, one must first sever delusion. Delusions are light and heavy: the heavy are called views, the light are called doubts. Even doubts must still be severed, how much more so views? Only the Buddha severs doubts; could they not ask?
Sengzong states: Prior to this, he taught only impermanence; now he clarifies the true principle of permanence. The teaching contradicts the past, so as a matter of course there should be doubt. Although the words do not point to it explicitly, the intent lies in this.
Baoliang states: This is the Tathāgata's final, ultimate teaching; hence he encourages them to ask.