Yoga Sutras of Patanjali · 4.18

सदाज्ञाताश्चित्तवृत्तयस्तत्प्रभोः पुरुषस्यापरिणामित्वात्॥१८॥

sadājñātāś cittavṛttayas tatprabhoḥ puruṣasyāpariṇāmitvāt

The modifications of the mind are always known to its lord, the purusha — because the purusha is unchanging.

— Yoga Sutras of Patanjali 4.18

Source: Sanskrit attributed to Patanjali (c. 2nd century BCE – 4th century CE). Public-domain English readings drawn from Swami Vivekananda's 'Raja Yoga' (1896) and Charles Johnston's 'The Yoga Sutras of Patanjali' (1912).