大般涅槃經集解 5.62

5.62

案僧亮曰：說定是無為者，說常以化人，所謂如上護法也。生善法者，以善化人，人得善命。是故如來致有長壽之報，如八河之歸海矣。生憐愍者，慈護物命，是長壽之因。

Sengliang comments: Declaring him definitely unconditioned means preaching permanence to transform people, which is what is called protecting the Dharma above. 'Giving rise to wholesome dharmas' means transforming people through goodness so that people attain wholesome life. Therefore the Tathāgata achieves the retribution of long life, just as the eight rivers return to the sea. 'Giving rise to pity' means lovingly protecting the lives of sentient beings, which is the cause of long life.