大般涅槃經集解 22.21

22.21

案僧亮曰：總以日月譬三寶滅也。法瑤曰：譬佛在世，人謂體盡丈六，是則無有常住法身。今明涅槃之後，故異上耳。

Sengliang states: It uses the sun and moon in general to illustrate the extinction of the Three Jewels. Fayao states: It illustrates that when the Buddha was in the world, people considered his substance to be exhausted by the sixteen-foot [body], which would mean there is no permanently abiding dharmakāya. Now it clarifies [the state] after nirvāṇa, which is why it differs from the above.