大般涅槃經義記 6.282

6.282

前中言「住無量劫」者，解有兩義：一就真論，世王不知如來常住所以悶絕，佛今為顯，令知佛常，是故名住至無量劫。二就應辨，應中有二：一對世王假設為言，若使世王重罪不滅，佛則為住至無量劫；彼罪若滅，不須佛住。二對世王流類以釋，世王流類廣多無盡，如來為之常在世間，不入涅槃，是故名住至無量劫。

Regarding the statement in the former section that he "dwells for incalculable kalpas," there are two interpretations: First, discussing from the absolute standpoint, the king fainted away because he did not know that the Tathāgata is eternally abiding; now the Buddha reveals this to cause him to know the Buddha's eternity, hence it is termed "dwelling for incalculable kalpas." Second, distinguishing from the standpoint of response: within the response there are two aspects: (1) speaking conditionally with respect to the king, if the king's grave offenses were not eradicated, the Buddha would dwell for incalculable kalpas for his sake; if those offenses are eradicated, there is no need for the Buddha to dwell. (2) Explaining with respect to those of the king's kind: those of the king's kind are vastly numerous and inexhaustible, and the Tathāgata is constantly in the world for their sake and does not enter nirvāṇa; hence it is termed "dwelling for incalculable kalpas."