Bhagavad Gita · Jnana Karma Sannyasa YogaChapter 4, Shloka 38 (4.38)

Two points. (1) Na hi jñānena sadṛśaṃ pavitram — nothing is as pure as knowledge; (2) svayaṃ … kālena ātmani vindati — one perfected through yoga finds it within, in time.

Shankaracharya: pavitraṃ pāvanaṃ śuddhi-karam (purifying, cleansing); yogena karma-yogena samādhi-yogena ca saṃsiddhaḥ saṃskṛtaḥ yogyatām āpannaḥ san mumukṣuḥ kālena mahatā ātmani vindati — the seeker of liberation, refined by karma-yoga and the yoga of samadhi and made fit, finds it in his own self after a long time.

Acharya Ramanuja: ātma-jñānena sadṛśaṃ pavitraṃ śuddhi-karam iha jagati vastv-antaraṃ na vidyate, tasmād ātma-jñānaṃ sarvaṃ pāpaṃ nāśayati — there is nothing else in this world as purifying as knowledge of the self; therefore it destroys all sin. Tat tathā-vidhaṃ jñānaṃ yathopadeśam ahar ahar anuṣṭhīyamānaṃ jñānākāra-karma-yogena saṃsiddhaḥ kālena svātmani svayam eva labhate — perfected through karma-yoga in the form of knowledge, practised day after day as taught, one gains that knowledge oneself, within, in due time.