八識規矩補註 2.23

2.23

This states that during the causal stage of the eighth consciousness, among the three natures it is solely of the anivṛtāvyākṛta nature, because it is not accompanied by afflictions, is impartial without conflict or resistance, and is that which is perfumed. When this consciousness cognizes an objective realm, its corresponding caittas are only the five sarvatragas, because the others are mutually contradictory. Why? The avyākṛta nature is neither wholesome nor unwholesome: if not wholesome, wholesome caittas do not correspond with it; if not unwholesome, unwholesome caittas also do not correspond with it; this is why they are mutually contradictory.