"These [third turning] sūtras teach that the dharmadhātu, that is, the intrinsically pure nature of the mind or buddha-element (khams), the essence of the Tathāgatas (the tathāgatagarbha), is primordially present in all beings. It is present from the very beginning and it is unchanging. Spontaneously, and from the very first, its appearing aspect is the source of the major and minor marks of the rūpakāya (the body of form); and its emptiness aspect is the dharmakāya (the body of ultimate reality) beyond all conceptual extremes. Since all enlightened qualities are naturally present within it, it is like a jewel; since it is unchanging, it is like space; and since it pervades all beings, as if moistening them, it is like water.

The nature of the mind is primordially luminous. As it is said in the Prajñāpāramitā in Eight Thousand Lines, “As for the mind, the mind does not exist; the nature of the mind is luminosity.” This is the buddha-element (khams) or potential (rigs) present in all beings."

Longchenpa