大乘起信論廣釋卷第三．四．五 3.56

3.56

論。云何五至不覺心動故　釋曰。次下辨釋。別釋五意。即分為五。此初也。名業識者。標其名也。即九相中第一業相。前對無明故為相。是無明體之相狀故。此對真心說名為識。依心所依意故。識成意故。下准此知。無明力者。舉所依緣也。明心不自起。起必有緣。不覺心動者。正明業義。謂起動義是業義故。

Treatise: "What are the five? [...] because the unawakened mind is stirred." Commentary: Next is the differentiation and explanation below, specifically explaining the five manas, which is divided into five parts. This is the first.

"Named karmic consciousness" designates its name—that is, the first, the characteristic of karma, among the nine characteristics. Previously, relative to avidyā it was a characteristic, being the manifestation of the substance of avidyā; here, relative to the true mind, it is called consciousness. Relying on the mind, it is the manas that is relied upon; the consciousness forms the manas. The subsequent ones should be understood accordingly.
"The power of avidyā" adduces the condition relied upon, clarifying that the mind does not arise of itself, but when it arises it must have conditions.
"The unawakened mind is stirred" directly clarifies the meaning of karma, because the meaning of stirring into activity is the meaning of karma.