首楞嚴義疏注經 1.541

1.541

若汝研窮此分別體，離六塵外實有性者，我即容許是汝真心。世人只知即心是佛，曾不仔細度量，此心剎那變異，猶如猿猴害馬，紛然亂想無暫停時。故《楞伽》云「當於靜處，觀此妄想流注生滅；凡夫不覺，妄謂不動。」故下經云「如瀑流水，望如恬靜，流急不見，非是無流。」《起信》亦云「一切眾生不名為覺，以從本已來念念相續，未曾離念，故說無始無明。」故佛再令微細揣摩，揩定真偽。

"If, when you investigate this differentiating substance to the utmost, it truly has an intrinsic nature apart from the six dusts, then I will grant that it is your true mind. People of the world only know that 'this mind is Buddha,' but have never carefully evaluated that this mind changes in every single kṣaṇa, just like an ape or a runaway horse, with confused thoughts fluttering about without pausing for an instant. Therefore, the Laṅkā[vatāra Sūtra] says: 'One should, in a quiet place, observe the flowing stream of arising and ceasing of these false thoughts; ordinary beings are not aware of it and falsely suppose it to be unmoving.' Thus, later in the sūtra it says: 'Like a torrential waterfall, it looks tranquil from afar, but its current is so rapid that it cannot be seen, not that there is no flow.' The Awakening of Faith also says: 'All sentient beings are not called enlightened, because from the beginningless origin, thought after thought continues unbroken, never having been apart from thought; therefore it is called beginningless avidyā.' Hence, the Buddha repeatedly urges us to subtly reflect and examine, to firmly determine the true from the false."