Perhaps again revealing thirty-two forms, and eighty kinds of excellences, with them naturally adorned, then manifesting Parinirvāṇa, as an analogy, this is like a lunar eclipse. Thus, for sentient beings, that seen is not the same, perhaps seeing half of the moon, perhaps seeing the full moon, perhaps seeing a lunar eclipse, yet this moon’s nature is truly without increase or decrease, of that in an eclipse ‘eaten’, there constantly is the full moon. The body of the Thus Come One is likewise thus, thus saying it constantly abides and does not change.
Great Parinirvāṇa Sūtra: 9th Scroll: The Thus Come One’s Nature’s Chapter 4 Of 6
How The Buddha Is Gone Yet Not Gone For Good