成唯識論述記 4.935

4.935

述曰：第八現起定恒依一依，常與一識俱轉故，即第七識，此通三界。在有色界亦依色根，即現行識，此不定故。有此二俱有依。

[The Commentary states:] The active eighth definitely and constantly relies on one support, because it always operates together with one consciousness, namely the seventh consciousness; this applies throughout the three realms. In the realm with form, it also relies on the physical sense-faculties, which refers to the active consciousness; this is not invariable. Thus, it has these two simultaneous supports.