Verse 4.10
तासामनादित्वं चाशिषो नित्यत्वात् ॥१०॥
tāsām-anāditvaṃ cā-āśisaḥ nityatvāt ||10||
Thirst for happiness beingeternal, desires are without beginning.
Just as the universe is eternal, so are impressions and desires. They have existed from time immemorial. For one whose seeds of defects are eradicated, and whose desires have come to an end, the upheavals of the universe appear to have come to an end.
Nobody knows the timeless, primeval, absolute One, or when the world came into being.
Both purusha and Prakriti spirit and nature, existed before man appeared. When creation took place, man was endowed with consciousness, intelligence, mind, senses of perception, organs of action and body. At the same time the characteristics or qualities (gunas) of nature, illumination (sattva) , action (rajas) and inertia (tamas) entered man's body.
Set on the wheel of time with the spokes of the gunas of nature, man began to function in accordance with these three fundamental, intermingling qualities. Though born with a pure heart, he gradually became caught in the web of nature and fell prey to the polarities of pleasure and pain, good and evil, love and hatred, the permanent and transient. That is how desires (vasana) and imprints (samskara) rooted themselves in man's life, and why this sutra says that desires have existed from time immemorial.
Through yoga sadhana, the desires that have existed since the beginning of time are eradicated so that kaivalya can be experienced.
In 2.12, Patanjali explained that the causes of actions are hidden accumulated impressions of our past deeds. In this chapter he speaks of pure actions, which collect and store no imprints.
The essential nature of citta is tranquillity, santa citta. When the sadhaka does not allow thought-waves to arise (vyutthana citta) , naturally there is no need for their restraint, nirodha citta. As both are filtered by santa citta, the sadhaka dwells in this quiet state and does his duties. His actions are pure, and their outcome too will be pure.
PATANJALI YOGA SUTRAS