大乘起信論廣釋卷第三．四．五 5.16

5.16

論。以垢無量至以為對治　釋曰。此顯眾行之所以也。真之理既遍一切無明遍真有不覺義。所詮垢遍一切法也。故非一行而能除遣。

Treatise: Because the defilements are limitless [...] to serve as an antidote.
Commentary: This reveals the reason for the multiple practices. Since the principle of the real pervades all, and avidyā pervades the real, there is the meaning of non-awakening. The defilements referred to pervade all dharmas; therefore, it is not by a single practice that they can be eliminated.