成唯識論述記 5.396

5.396

述曰：第三師言：第二師說亦不應理。此無始來，一由任運故恒；二由一類故無變，故唯捨受；非是捨受可名變異，有易脫故。《瑜伽》六十三證俱生捨受，第八識俱，非可起餘憂、喜等受，亦證此義。然樂、憂等皆思惟引發，此識任運，如何不起捨？

The Commentary states: The third master says: The explanation of the second master is also unreasonable. From beginningless time, first, this consciousness is constant because it functions spontaneously; second, it lacks change because it is of a uniform category; therefore it has only equanimity feeling; it is not that equanimity feeling could be called mutative, since it possesses alteration. The sixty-third fascicle of the Yogācārabhūmi proves that innate equanimity feeling is conjoined with the eighth consciousness and cannot give rise to other feelings such as grief or joy, which also proves this point. However, pleasure, grief, and the like are all induced by reflection; since this consciousness is spontaneous, how could it not give rise to equanimity?