सदाज्ञाताः चित्तव्र्त्तयः तत्प्रभोः पुरुषस्यापरिणामित्वात् ॥१८॥
sadajnatah chitta vrttayah tat prabhoh purushasya aparinamitvat ||18||

[RA] 4.18 The true self can always observe the misconceptions (vritti) in that which is mutable in human beings, because this pure self (purusha) is not in motion.

[JW] 4.18 Unintermittently the Master of that [mind-stuff] knows the fluctuations of mind-stuff [and thus] the Self undergoes-no-mutations.

[SS] 4.18 Due to His changelessness, changes in the mind-stuff are always known to the Purusha, who is its Lord. [p216]

[EB] 4.18  The permutations of the mind are always known to its master, the purusa soul, because of the soul's unchanging nature. [p436]

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sadā = always

jñātāḥ = known

citta = all that is mutable in human beings; mind; spirit

vṛttayaḥ = waves; thought waves, misconceptions

tat-prabhoḥ = from one’s master; master

puruṣasya = the true self; drashtu

aparinamitvat = owing to immutability