Well then, one may wonder, because of what reason are sentient beings possessors of the essence of the buddhas?

Since the dharmakaya pervades sentient beings through emptiness; since there is no distinction within the suchness of phenomena themselves; since all sentient beings have the buddha nature; therefore, since there are three reasons, sentient beings are endowed with the essence of the buddhas. Like that, moreover, as it says in the Uttaratantra Shastra: “Since the body of complete buddhahood is all-pervasive, since suchness is without division, since there is the presence of buddha nature, all beings are always endowed with the essence of the buddhas.”

-- Gampopa