大乘起信論義記 3.80

3.80

言唯心相滅非體滅者，境界滅時，唯心麁相滅，非心自體滅。又以無明滅時，唯心細相滅，亦非心體滅。此通答二問也。喻中別顯此二。

Saying 'only the marks of the mind cease, not the substance that ceases': when perceptual objects cease, only the coarse marks of the mind cease, not the intrinsic substance of the mind that ceases. Furthermore, when avidyā ceases, only the subtle marks of the mind cease, and it is also not the substance of the mind that ceases. This universally answers both questions. In the simile, both are individually illustrated.