大乘起信論義記 3.13

3.13

In the answer there are three parts: first, being identical with purity, it is constantly defiled; second, from "although there is a defiled mind" downward, being identical with defilement, it is constantly pure; third, from "therefore" downward, concluding that it is difficult to fathom, hence only the Buddha knows it. In the first part there are three phrases.