首楞嚴義疏注經 10.16

10.16

性入元澄者，行陰若盡，遷流性澄，歸一藏識，名入元澄。經云「藏識海常住」也。以觀行增勝，能純生滅根元習氣，令其不動，歸一識陰，猶如澄水也。以行是眾生遷流業性故，此若盡即超眾生濁也。行陰生滅微細難覺，故名幽隱。

"The nature entering the primal clarity" means that if the aggregate of volitional formations is exhausted, the fluctuating nature becomes clear and returns to the single storehouse consciousness (ālaya-vijñāna); this is called entering the primal clarity. The sūtra states, "The ocean of the storehouse consciousness is permanently abiding." Through the increasing superiority of contemplative practice, one can purify the primal habit-energy of arising and ceasing, causing it to remain unmoving and return to the single aggregate of consciousness, just like clear water. Because volitional formations are the fluctuating karmic nature of sentient beings, if these are exhausted, one then transcends the turbidity of sentient beings. Arising and ceasing in the aggregate of volitional formations are subtle and difficult to perceive; therefore they are called "hidden."