成唯識論述記 5.977

5.977

述曰：彼地獄等苦根，意識俱者，與餘雜受處及人天中，憂根相似，亦在意識逼迫受故，說彼苦根為憂，實非憂受。問：若爾，第三定樂似餘地意識中喜，應名喜根。為決此疑，更今應解。

The Commentary states: That pain faculty in hell and so forth which is associated with the mental consciousness is similar to the sorrow faculty in other places of mixed feeling and among humans and devas, because it is also an oppressive feeling in the mental consciousness; therefore that pain faculty is called sorrow, but it is not truly sorrow feeling. Question: If so, the pleasure in the third dhyāna is similar to joy in the mental consciousness of other stages, so it should be called the joy faculty. To resolve this doubt, it must now be further explained.