Trikāya

The Trikāya doctrine (Sanskrit, literally "Three bodies"; 三身 Chinese: Sānshēn Vietnamese: Tam thân, Japanese: Sanjin or Sanshin, Tibetan: སྐུ་གསུམ, Wylie: sku gsum) is a Mahayana Buddhist teaching on both the nature of reality and the nature of Buddhahood.

The doctrine says that a Buddha has three kāyas or bodies:

Even before the Buddha's parinirvāṇa, the term Dhammakāya was current. Dhammakāya literally means Truth body.

In the Pāli Canon the Buddha tells Vasettha that the Tathāgata (the Buddha) was Dhammakāya, the 'Truth-body' or the 'Embodiment of Truth', as well as Dhammabhuta, 'Truth-become', 'One who has become Truth'

The Buddha is equated with the Dhamma:

... and the Buddha comforts him, "Enough, Vakkali. Why do you want to see this filthy body? Whoever sees the Dhamma sees me; whoever sees me sees the Dhamma."

In the Aggañña Sutta the Buddha advises Vasettha that whoever has strong, deep rooted, and established belief in the Tathagatha, he can declare that he is the child of Bhagavan, born from the mouth of Dhamma, created from Dhamma, and the heir of Dhamma. Because the titles of the Tathagatha are: The Body of Dhamma, The Body of Brahma, the Manifestation of Dhamma, and the Manifestation of Brahma.

The Dharmakāya doctrine was possibly first expounded in the Aṣṭasāhasrikā Prajñāpāramitā "The Perfection of Wisdom In Eight Thousand Verses", composed in the 1st century BCE.

...
Wikipedia