仁王護國般若波羅蜜多經疏 2.606

2.606

解曰：諸佛未成佛者，明在因也。與當佛為智母者，謂前實相即是本覺。因中本覺為無明覆，望後當果必正智圓，與自當佛為智因也。如如意寶，垢穢暫時，垢盡體圓，說初為母。諸佛已成佛即為一切智者，明果德圓。覺解圓極，即為智也。未得為性已得為智者，辯因果也。因中障覆即為佛性，果德顯現名一切智。

Explanation: "When all buddhas have not yet attained buddhahood" clarifies the stage of the cause. "It serves as the mother of cognition for the future buddhas": this means that the aforementioned true mark is innate enlightenment. In the cause, innate enlightenment is covered by ignorance; looking forward to the future fruit, correct cognition will certainly be perfected, serving as the cause of cognition for one's own future buddhahood. It is like a wish-fulfilling jewel whose defilement is temporary; when the defilement is exhausted, its substance is complete, so the initial state is called the mother. "When all buddhas have already attained buddhahood, it is precisely all-knowledge" clarifies the perfection of the fruitional virtue. When awakening and understanding reach the ultimate perfection, it is precisely cognition. "Not yet attained, it is the nature; already attained, it is cognition" distinguishes the cause and fruit. Covered by hindrances in the cause, it is the buddha-nature; when fruitional virtue is manifested, it is called all-knowledge.