大乘起信論義記 2.155

2.155

答意云：業等染心名諸識相，此等皆是不覺之相，故云心識之相皆是無明，非約心體說也。

The intent of the answer is: The defiled minds such as the karmic [consciousness] are called the marks of the various consciousnesses; all these are the marks of non-enlightenment. Therefore, it is said that 'the marks of the mind and consciousness are avidyā,' which is not spoken with regard to the substance of the mind.