俱舍論疏 3.165

3.165

論「阿羅漢果至依因性故」，釋後果也。二道相資，如初果釋。雖樂、喜、捨三根容得，正得果時唯一受故，不越九根。雖無間、解脫道不同時，而等流、士用果同時故，亦無有過。

The treatise says: "The fruit of the arhat ... because of the nature of being a supporting cause." This explains the final fruit. The two paths mutually support each other, as explained for the first fruit. Although the three faculties of pleasure (sukha), joy (saumanasya), and equanimity (upekṣā) are all admissible for attainment, at the exact time of attaining the fruit there is only a single sensation (vedanā), so it does not exceed nine faculties. Although the uninterrupted path and the path of liberation are not simultaneous, since the fruitional effect of outflow (niṣyandaphala) and the virile effect are simultaneous, there is also no fault.