八識規矩補註 2.9

2.9

謂此識恒常審推、思察、量度第八見分為我，故云爾也。恒之與審，於八識中四句分別：一、恒而非審，謂第八識不執我無間斷故；二、審而非恒，謂第六識以執我間斷故；三、亦恒亦審，謂第七識執我無斷故；四、非恒非審，謂前五識不執我故。故護法菩薩云「五八無法亦無人，六七二識甚均平」，是也！

This means that this consciousness constantly and persistently investigates, scrutinizes, and deliberates upon the darśanabhāga of the eighth [consciousness] as a self; hence it is stated as such. As for "constantly" and "examining," they are distinguished among the eight consciousnesses according to four propositions: 1. Constant but not examining, which refers to the eighth consciousness, because it does not grasp a self and is without interruption; 2. Examining but not constant, which refers to the sixth consciousness, because its grasping of a self has interruptions; 3. Both constant and examining, which refers to the seventh consciousness, because its grasping of a self is without interruption; 4. Neither constant nor examining, which refers to the first five consciousnesses, because they do not grasp a self. Thus Bodhisattva Dharmapāla said: "The fifth and eighth have neither dharma nor person; the two consciousnesses, the sixth and seventh, are extremely balanced." This is just it!