成唯識論演祕 6.358

6.358

釋曰：從染觀待至染定別，總名染法同事因也。又若清淨品觀待因乃至定別，彼望清淨為同事因。

The explanation says: from the defiled relational [cause] up to the defiled determining [cause], they are collectively called the co-functioning cause of defiled phenomena. Furthermore, if they are the relational cause up to the determining cause of the purified class, they are the co-functioning cause in relation to purification.