俱舍論疏 4.180

4.180

論「復有釋言至而體是一」，述異說也。界是性義、因義。淨、不淨品緣境差別，作種種因差別不同，故名為心。如一樹心與大小枝葉種種不同而為界性。餘文易了。

On the Śāstra's [words], "There is another explanation […] yet their entity is one": this relates an alternative explanation. Realm (*dhātu*) has the meaning of nature and the meaning of cause. The pure and impure categories differ in observing objects, producing different causes that vary; therefore it is called mind (*citta*). Just as the single core of a tree serves as the nature/realm for various different large and small branches and leaves. The rest of the text is easy to understand.