金光明經玄義 1.18

1.18

云何三佛性？佛名為覺，性名不改。不改即是非常非無常，如土內金藏，天魔外道所不能壞，名正因佛性。了因佛性者，覺智非常非無常，智與理相應，如人善知金藏，此智不可破壞，名了因佛性。緣因佛性者，一切非常非無常，功德善根資助覺智、開顯正性，如耘除草穢掘出金藏，名緣因佛性。當知三佛性一一皆常樂我淨，與三德無二無別。既以金光明譬三德，還以金光明三字譬三佛性也。

What are the three kinds of buddha-nature? "Buddha" means awakened; "nature" means unchangeable. Unchangeable means neither permanent nor impermanent; like a store of gold within the earth, which celestial demons and outsiders cannot destroy, it is called the direct cause buddha-nature. As for the revealing cause buddha-nature: awakened wisdom is neither permanent nor impermanent; wisdom corresponds with the principle, like a person who well knows the gold store; this wisdom cannot be destroyed, and is called the revealing cause buddha-nature. As for the conditional cause buddha-nature: all are neither permanent nor impermanent; merits and wholesome roots assist the awakened wisdom to reveal the direct nature, just like weeding away refuse and digging out the gold store; it is called the conditional cause buddha-nature. One should know that each and every one of the three kinds of buddha-nature is permanence, bliss, self, and purity, neither dual nor distinct from the three virtues. Since the Suvarṇaprabhāsa serves as a metaphor for the three virtues, the three characters of Suvarṇaprabhāsa also serve as a metaphor for the three kinds of buddha-nature.