成唯識論述記 5.484

5.484

述曰：彼說八識皆有執故，不可說執依第八識，第八識俱無惠執故，非八俱也。

The Commentary states: Since they say that all eight consciousnesses have grasping, one cannot say that this grasping depends on the eighth consciousness, because the eighth consciousness is not accompanied by discerning grasping, and hence it does not accompany the eighth.