大般涅槃經義記 3.301

3.301

上來合竟。「如來祕藏如是無量不可思」者，是第三段結歎經勝，由經見性，所以歎之。《大涅槃經》名為祕藏，所辯義廣故言無量，所顯義深名不可思。亦可此言結歎佛性，性名祕藏，廣名無量，深名不思。

The application above is now complete. "The Tathāgata's secret treasury is immeasurable and inconceivable like this" is the third section concluding with praise of the sūtra's superiority; because one sees the nature through the sūtra, it is therefore praised. The *Mahāparinirvāṇa Sūtra* is called the secret treasury; because the meanings it explains are extensive, it is said to be immeasurable; because the meanings it reveals are profound, it is called inconceivable. Alternatively, these words conclude with praise of the buddha-nature: the nature is called the secret treasury, its breadth is called immeasurable, and its depth is called inconceivable.