大乘起信論廣釋卷第三．四．五 5.72

5.72

Treatise: "This correct mindfulness... is unobtainable."
Commentary: This shows the reason. That is, someone might doubt: why is non-thought called "collecting it" and "abiding in correct mindfulness"? Therefore, it shows correct mindfulness and explains its reason. Separating from both kinds of mind, with nothing to obtain, and契-verifying tathatā: this is the characteristic of correct mindfulness.
"Still only mind..." and so forth means there is no grasped object. "Then again this mind..." and so forth means there is no grasping subject. Since one separates from both mind and object, it attains the name "correct mindfulness"; therefore, merely having no thought is called "collecting it," for separated from the real, there is no characteristic of correct mindfulness. Therefore the new version says: "When the mind wanders to external objects, collect it to abide in the internal mind; afterwards, when the mind arises again, do not grasp mental signs, because separated from tathatā it is unobtainable." Therefore various treatises say: "The skilful instruction says that when the bodhisattva is in the state of absorption, he contemplates images as being only the conceptual signs of mind. Once the empty contemplation decreases, only its own characteristic remains. Thus abiding in the internal mind, he knows that the grasped does not exist; next, the grasper is also non-existent; afterwards [...] there is nothing to be eliminated."