Patanjali Yoga Sutras
Sutra 2.20
The indweller is pure consciousness only, which though pure, sees through the mind and is identified by ego as being only the mind.
Conscious intelligence is the eternal light of awareness by which everything else is known, and has the power to know itself. Consciousness itself is the life of sentiency; it is how we are alive. The mind is confused about this, however, and believes it is the seer. The mind (antahkarana) is comprised of Buddhi (intellect), manas (root of desires) and ahamkara (ego). Of these, Buddhi, the thinker, thinks it has awareness. But it is consciousness that becomes the Buddhi, contracted by the objects of perception. Buddhi is ephemeral prakriti, consciousness is eternal Purusha. Buddhi dies with the body, consciousness is untouched by death. More immediate than that, in the stillness of no thought, the mind goes utterly out of existence; the mind being no different than the thoughts it thinks. The Buddhi notices this and, being the discriminative faculty, realizes the truth that the mind is not the Self. Thus begins the awakening of the yogi to the path of liberation (kaivalya).
One of my favorites, thank you for posting and helping me remember.