大乘起信論義記 2.199

2.199

後文中二：初、明妄有起淨之功；後、明真有待妄之義。良以依真之妄方能顯真，隨妄之真還待妄顯故也。

In the latter text, there are two: first, explaining that delusion has the efficacy of giving rise to purity; second, explaining that the real has the meaning of depending on delusion. Truly, it is because delusion relying on the real can only then reveal the real, and the real conforming to delusion in turn depends on delusion to be revealed.