Mandukya Karika, verse 3.30

Sanskrit text, IAST transliteration and English translation

अद्वयं च द्वयाभासं मनः स्वप्ने न संशयः ।
अद्वयं च द्वयाभासं तथा जाग्रन्न संशयः ॥ ३० ॥

advayaṃ ca dvayābhāsaṃ manaḥ svapne na saṃśayaḥ |
advayaṃ ca dvayābhāsaṃ tathā jāgranna saṃśayaḥ || 30 ||

30. There is no doubt that the mind, which is, in fact, non-dual appears as dual in dream; in like manner undoubtedly that which is non-dual, appears as dual in the waking state also.

Shankara Bhashya (commentary)

Really speaking, the snake is identical with the rope. In like manner, the mind which is nondual¹ as Ātman appears undoubtedly in dual forms in dreams. Verily in dream, such objects of perception as elephants, etc., or their perceivers such as eyes, etc., have² no existence independently of consciousness (mind). Similar³ is the case in the waking state as well. For (conciousness) mind, which is the highest Reality, is common to both.

Anandagiri Tika (glossary)

The opponent may contend that the previous Kārikā admits duality. This Kārikā shows that the perception of duality is due to our ignorance. The only Reality, both in the dream and the Waking states, is mind or consciousness which appears as dual, i.e., the perceiver and the perceived, on account of ignorance.

¹ Non-dual, etc.—This is known in Suṣupti or deep-sleep when the mind remains as pure and non-dual.

² Have, etc.—That the perceiver and the perceived in the dream state have no existence independent of the mind is known in the waking state.

Similar, etc.—In the waking state also what is perceived is only the act of the mind. The same consciousness is common in both the states. The idea of a mind having the dual characteristics of determination and volition is superimposed upon the substratum, i.e., consciousness; and as a result, the phenomenal world is perceived. It should not be thought that there is any other cause for the appearance of duality excepting ignorance.