大般涅槃經義記 9.17

9.17

Next, it symbolizes nirvāṇa in terms of the time of the fifteenth day. Siṃhanāda asks first: "The four times, such as birth, all occurred on the eighth day; why is nirvāṇa alone on the fifteenth day?" Below, the Buddha first praises [the question] and then explains it. Within the explanation, there are three points: First, "at the time of the fifteenth day, the moon has neither waning nor waxing," symbolizing that the Buddha's nirvāṇa has neither waning nor waxing. Second, "at the time of the fifteenth day, the moon is fully rounded for eleven matters," revealing that the Buddha's virtues are complete, benefiting sentient beings through eleven matters. Third, from "I truly do not enter..." onward, it explains in connection with the first section that the Buddha is not extinguished, though foolish people think he is extinguished; first [explaining] the doctrine, and then the simile.