俱舍論記 2.204

2.204

「十八界中至法餘餘界」者，十八界中，法界中一分是常，謂三無為。義准無常，即法界中除三無為諸餘法界，故言法餘及餘十七界也。

Regarding [the passage] "Among the eighteen dhātus... the remainder of the dharma-[dhātu] and the remaining dhātus": among the eighteen dhātus, one portion of the dharma-dhātu is eternal, namely the three unconditioned [dharmas]. By implication, the impermanent are the remaining dharma-dhātus in the dharma-dhātu excluding the three unconditioned [dharmas]; therefore it says "the remainder of the dharma-[dhātu] and the remaining seventeen dhātus."