成唯識論演祕 5.505

5.505

釋曰：由樂、喜、捨通第六識，六識樂、喜未位之時而亦有捨，故云一切未位等也。又云：疑於欲界非喜相應者，不決定心若未息滅，喜不生故。又云：何故煩惱皆捨相應？以一切煩惱隨中庸位方息沒故，所以者何？煩惱生起，展轉相續，漸漸微薄勢力將盡，隨處中位，於此位中必捨相應。

Explanation: Because pleasure, joy, and equanimity apply to the sixth consciousness, at the terminal phase of pleasure and joy in the sixth consciousness there is also equanimity, hence it says 'in all terminal phases,' and so forth. It also says: As for doubt in the desire realm not associating with joy, if an indecisive mind has not subsided, joy does not arise. It also says: Why do all afflictions associate with equanimity? Because all afflictions subside and vanish only in an intermediate stage. Why is this? When afflictions arise and continue uninterruptedly, they gradually become subtle and weak, and their power is about to be exhausted; as they reach an intermediate stage, at this stage they necessarily associate with equanimity.