It’s sort of like “trickle-down” afterlife.
In even very ancient henotheistic Judaism, Enoch and Elijah are taken directly up, alive, into God’s heaven.
Eventually, this trickles down to everyone. Like in Egyptian religion.
This has something of a parallel in “trickle-down” Buddha-nature.
At one point, the dhātu was found in the cremated remains of sages. The belief was that, through their supreme practice in their life, they had sort-of ‘trasmuted’ a part or parts of their bodies into something permanent and deathless, or at least significantly more permanent than their corpses. These would then be distributed to various temples, pilgrimage attractors, etc, and would be venerated as relics. “This is what the wise can achieve”, sort-of like.
We can see an echo of this practice in the Lotus Sūtra:
parinirvṛtaṃ dṛṣṭva mamātmabhāvaṃ
dhātūṣu pūjāṃ vividhāṃ karonti|
māṃ cā apaśyanti janenti tṛṣṇāṃ
tatorjukaṃ citta prabhoti teṣām||5||
Many see me, I pass into extinguishment,
widely they worship my relics,
sweetly, their hearts, each and every,
wish to look upon my heart with reverence.
(Saddharmapuṇḍarīkanāmamahāyānasūtra, Nepalese recension, English based on Kumarajīva recension, note that relics is “dhatu” in the Sanskritic recension.)
Over time, in Mahāyāna Buddhism, it seems that the belief comes to be that all beings have these dhātavaḥ. And eventually, down the line, we have Buddha-nature doctrines that proclaim the ordinary sentient being to be “already enlightened” in some way, sharing in the qualities of the Tathāgata, sometimes proclaiming every sentient being as equal to the Tathāgata:
At that time, the Buddha sat up straight in meditation in the sandalwood pavilion and, with his supernatural powers, put on a miraculous display. There appeared in the sky a countless number of thousand-petaled lotus flowers as large as chariot wheels, filled with colors and fragrances that one could not begin to enumerate. In the center of each flower was a conjured image of a Buddha. The flowers rose and covered the heavens like a jeweled banner, each flower giving forth countless rays of light. The petals all simultaneously unfolded their splendor and then, through the Buddha’s miraculous powers, all withered in an instant.
Within the flowers all the Buddha images sat cross-legged in the lotus position, and each issued forth countless hundreds of thousands of rays of light. The adornment of the spot at the time was so extraordinary that the whole assembly rejoiced and danced ecstatically. In fact, it was so very strange and extraordinary that all began to wonder why all the countless wonderful flowers should suddenly be destroyed. As they withered and darkened, the smell they gave off was foul and loathsome.
[…]
The Buddha said, ‘Good sons, there is a comparison that can be drawn between the countless flowers conjured up by the Buddha that suddenly withered and the innumerable conjured buddha images with their many adornments, seated in the lotus position within the flowers, who cast forth light so exceedingly rare that there was no one in the assembly who did not show reverence.
‘In a similar fashion, good sons, when I regard all beings with my buddha eye, I see that hidden within the kleśāḥ of greed, desire, anger, and stupidity there is seated augustly and unmovingly the Tathāgata’s wisdom, the Tathāgata’s vision, and the Tathāgata’s body. Good sons, all beings, though they find themselves with all sorts of kleśāḥ, have a Tathāgatagarbha that is eternally unsullied, and that is replete with virtues no different from my own.
‘Moreover, good sons, it is just like a person with supernatural vision who can see the bodies of Tathāgatāni seated in the lotus position inside the flowers, even though the petals are not yet unfurled; whereas after the wilted petals have been removed, those Tathāgatāni are manifested for all to see. In similar fashion, the Buddha can really see the Tathāgatagarbhāḥ of sentient beings. And because he wants to disclose the Tathāgatagarbha to them, he expounds the sutras and the Dharma, in order to destroy kleśāḥ and reveal Buddha-nature.
(Tathāgatagarbhasūtra)
迦葉菩薩白佛言:「世尊!我從今日始得正見。世尊!自是之前,我等悉名邪見之人。
Mahākāśyapa Bodhisattva asked the Buddha to speak: "Bhagavān! I from today start in obtaining samyagdṛṣṭi. Bhagavān! Until now, we all entirely abided in mithyādṛṣṭi.
世尊!二十五有,有我不耶?」
Bhagavān! In the twenty five existences, is there ātman definitely?
佛言:「善男子!我者即是如來藏義。一切眾生悉有佛性,即是我義。
The Buddha said: "Kulaputra! Ātman, prompt and exact, is Tathāgatagarbha in meaning. All sentient beings in entirety have the Buddha’s nature, prompt and exact, ātman is it’s meaning.
如是我義,從本已來,常為無量煩惱所覆,是故眾生不能得見。
Thus so ātman’s meaning is, from root proceeding onwards, constantly without limit under kleśāḥ covered, therefore sentient beings cannot obtain sight of it.
(Mahāyānamahāparinirvāṇasūtra Dharmakṣema recension)
Am I alone in seeing something of a relation?
This is one of the fancy containers that dhātavaḥ were/are venerated in:
Just for some added historical context.