Zen master Dogen, along with other Mahayana teachers, taught that the universe itself is Buddha-nature.
Rather than something we have like a soul or spirit, Buddha-nature is instead what we are as particular manifestations of the one universal Buddha-nature, Existence itself:
For Dōgen, Buddha-nature or Busshō (佛性) is the nature of reality and all Being. In the Shōbōgenzō, Dōgen writes that “whole-being (Existence itself) is the Buddha-nature” and that even inanimate things (grass, trees, etc.) are an expression of Buddha-nature. He rejected any view that saw Buddha-nature as a permanent, substantial inner self or ground. Dōgen held that Buddha-nature was “vast emptiness”, “the world of becoming” and that “impermanence is in itself Buddha-nature”. According to Dōgen:
Therefore, the very impermanency of grass and tree, thicket and forest is the Buddha nature. The very impermanency of men and things, body and mind, is the Buddha nature. Nature and lands, mountains and rivers, are impermanent because they are the Buddha nature. Supreme and complete enlightenment, because it is impermanent, is the Buddha nature.
Humans, plants and animals, rather than separate living things which each have a Buddha-nature, are temporary manifestations of the one Buddha-nature, which is none other than the totality of Existence itself.
This does away with the distinction between the material and the spiritual, since they are instead seen as different aspects of the same reality. The experience of enlightenment is realizing the interconnectedness of all things (dependent origination), that we are not separate or distinct from the Whole.
The reason why I am sharing these things is to show that the concept of Buddha-nature, when seen as another way of describing the totality of Existence itself, in no way contradicts the Buddha’s original teachings on impermanence and anatta or non-self.