Yoga Sutra - Sādhana Pada 2.11
ध्यान हेयाः तद्वृत्तयः ॥११॥
dhyāna-heyāḥ tat-vṛttayaḥ ||11||
Their fluctuations are to be voided by meditation.
The states of mind produced by these kleśas are eliminated by meditation.
We had suggested at the beginning of the chapter that the relationship of yoga defined in I.2 as citta-vṛtti-nirodha, with kriyā-yoga as defined in II.1, is that by the former the vṛttis are weakened, and by the latter the kleśas or mechanisms underpinning the production of the vṛttis are eliminated. By the phrase tad-vṛttayaḥ, Patañjali here confirms that the kleśas produce the vṛttis. They are thus a deeper element of the psyche and unavoidably need to be confronted if one wishes to nirodha the vṛttis produced by them, as I.2 requires the yogī to do.
Patañjali indicated in II.2 that the kleśas are destroyed by kriyā-yoga, yet here he states that the vṛttis produced by them are destroyed by meditation, dhyāna. Vyāsa clarifies that the seed power, or fructifying ability, of the kleśas is weakened by the practice of kriyā-yoga and then eradicated by the practice of meditation, until they become like burnt seeds. He gives the useful example of washing garments: gross dirt is first removed from soiled clothes, and then efforts are directed at the finer dirt. In the same way, the gross manifestations of the kleśas can be easily removed by kriyā-yoga, but the more subtle ones require greater efforts.
The commentators understand the process of eradicating the kleśas as a threefold sequence: First the cloth is cleaned by shaking it in the air or washing it in water, and this removes the larger chunks of dirt. It is then washed more carefully by adding a cleaning agent or beating it against a stone (as is still the custom in India), and this removes the finer, more ingrained dirt. But to completely and absolutely remove all subtle impressions of the soiled spots, says Rāmānanda Sarasvatī, you ultimately have to destroy the cloth itself. Likewise, the grosser aspects of the kleśas are eliminated by kriyā-yoga, the more subtle aspects by meditation, but, as indicated by the last sūtra, the actual burnt seeds, or residual impressions of the now impotent saṁskāras, are not completely dissolved until the mind, along with all its latent saṁskāras, merges back into its matrix at the death of the yogī who has attained the highest state of samadhi.