大方廣圓覺修多羅了義經略疏 1.571

1.571

Now, as for the first: calling it the doctrinal basis is because Samantabhadra merely inquired about cultivating illusion, not about where illusion arises. When the Buddha states that it is born in the mind of enlightenment, this is not yet the direct answer to what was asked. Yet he first needs to indicate this as the basis, relying on which he reveals that when illusion is exhausted enlightenment is perfect; thus the meaning of cultivating illusion can be established. When illusion is exhausted, it is fundamentally not annihilation. Therefore the Śāstra states: “The inherently pure mind is stirred by the wind of avidyā, up to: when avidyā is extinguished, the nature of wisdom is not destroyed. Just as when the wind ceases the motion is extinguished, but the nature of wetness is not destroyed,” and so forth.