金光明經文句記 5.198

5.198

初、對初家五性。安樂性即正因佛性者，安樂乃是涅槃之義，具足三法；今就合說，但名正因。世出世等者，六道是世間因果，三乘是出世因果。言因佛性者，境界之性但齊九界十如，是法望佛是因，以其佛界十如，是法望九稱果，皆屬能觀，不名境界。故《起信論》但以九相而為境界。是故業相名細中細，為佛境界。又云「依轉識故說名境界，而此證者無有境界可說。」故知境界是九界法。若爾，何名佛性？良以果人不獨成就佛界十法，亦能成就九界十法，是故千法。眾生雖具，體用不彰；唯佛究竟圓融自在，所以因法是果人性。

First, matching the first house's five natures. 'The nature of peace and bliss is the direct-cause Buddha-nature': peace and bliss is the meaning of nirvāṇa, complete with the three dharmas; here, speaking of them combined, it is named only direct cause. Regarding 'mundane and supramundane', etc.: the six destinies are mundane cause and effect; the three vehicles are supramundane cause and effect. As for the 'cause Buddha-nature': the nature of the realm only covers the ten suchnesses of the nine realms; these dharmas, viewed from the perspective of the Buddha, are cause; because the ten suchnesses of the Buddha realm, viewed from the nine realms, are called fruit, they all belong to that which can contemplate and are not named realm. Therefore the Awakening of Faith takes only the nine marks as realm. Hence the karma mark is called the subtlest of the subtle, being the Buddha's realm. It also says: 'Relying on the evolving consciousness, it is spoken of as realm; but for one who realizes this, there is no realm that can be spoken of.' Thus we know that realm is the dharma of the nine realms. If so, why is it called Buddha-nature? Truly it is because the person of the fruit not only accomplishes the ten dharmas of the Buddha realm, but also accomplishes the ten dharmas of the nine realms; therefore, regarding the thousand dharmas: although sentient beings possess them, essence and function are not manifest; only the Buddha is ultimate, perfectly integrated, and autonomous, and so the causal dharmas are the nature of the person of the fruit.