大乘起信論裂網疏 3.74

3.74

謂第八識中無明種子，只須一念不覺，便起現行而生染心。此雖等覺菩薩，未轉異熟識為無垢識，尚未能盡其源。唯佛位中，既與大圓鏡智相應，方能通達其性相之邊底也。初總明義深竟。

This means that as for the seeds of ignorance in the eighth consciousness, merely by a single thought of non-enlightenment, active manifestations arise and produce the defiled mind. Even for a bodhisattva of equal enlightenment, who has not yet transformed the ripening consciousness into the taintless consciousness, its source cannot yet be exhausted. Only in the Buddha stage, having associated with the great round mirror wisdom, can one thoroughly penetrate the very bounds and depths of its nature and characteristics. The first part, explaining in general the profundity of the meaning, is concluded.