Yoga Sutras of Patanjali translated by Yogi Kalinath - Chapter 4, Verse 18
Pada 4, Sutra 18
Sadaa jnaataash citta-vrttayas tat-prabhoh purusasyaaparinaamitvaat
Due to the Self, the Purusha, the Master of the mind, being unchangeable, the mind’s fluctuations, the vrittis, are always known to it.
The Self is the Regent. It is the Witnessing Consciousness that give rise to awareness of movement within the mind. It is unaffected by either gross or subtle changes in one’s external or internal environments. This Self, the Purusha is unchangeable and therefore is aware of all fluctuations in the phenomenal world of Prakriti.
The Seer abides in the Self and is able to witness all fluctuations on the mirror of consciousness as the Play of Shiva Shakti, the simultaneous interaction and flow of the wave and particle state.