"The [dharmakaya] is purity, since its nature is pure and [even] the remaining imprints are fully removed.
It is true self, since all conceptual elaboration in terms of self and non-self is totally stilled.
It is true happiness, since [even] the aggregates of mental nature and their causes are reversed.
It is permanence, since the cycle of existence and the state beyond pain are realized as one."

Mahāyānottaratantra Śāstra;