大般涅槃經義記 6.226

6.226

下次對上第四句難明迦葉佛不說名滅，法實不滅，故得名為諸佛祕藏，先辯、後釋。

Next, in response to the dilemma in the fourth clause above, he clarifies that for Kāśyapa Buddha, not preaching it is called extinction, but the Dharma in reality is not extinguished; hence it can be named the secret treasury of the buddhas. First he explains, and afterward interprets.