成唯識論述記 7.696

7.696

述曰：五識中初三識，上下言自類互為緣，後二識但言自類為緣，不可言互，唯一界故，此唯有漏，此言善等亦隨所應上下界地。

The Commentary states: Among the five consciousnesses, the first three consciousnesses are said, in terms of higher and lower stages, to serve as conditions mutually for their own kind. The latter two consciousnesses are only said to serve as conditions for their own kind; they cannot be said to do so mutually, because they exist in only one realm. These are solely sāsrava. The reference here to wholesome, etc., also corresponds appropriately to higher and lower realms and stages.