瑜伽論記 20.246

20.246

言微細、極微細等者，此有兩解。一云，凡夫不能見故云微細，二乘不能窮底，故云甚深、極甚深，解了地無不能通達，故云難通、達極通達。二云：世間聞思修慧，如次配釋也。

As for the words "subtle, extremely subtle," etc.: there are two explanations for this. One says: ordinary beings cannot see it, hence it is called "subtle"; the two vehicles cannot fathom its depths, hence it is called "profound, extremely profound"; and there is nothing on the stage of understanding that cannot be penetrated, hence it is called "difficult to penetrate, extremely [difficult] to penetrate." The second says: worldly wisdoms derived from listening, reflecting, and cultivating are matched and explained respectively.