大乘起信論義記 2.267

2.267

三者、名為現識，所謂能現一切境界，猶如明鏡現於色像；現識亦爾，隨其五塵對至即現，無有前後，以一切時任運而起常在前故。

[The text states:] "The third is named manifesting consciousness, meaning that it is able to manifest all sense-objects, just as a bright mirror manifests visible forms; the manifesting consciousness is also like this: following the five dusts, as they confront it, it immediately manifests them without prior or posterior, because at all times it arises spontaneously and is always in front."