Bhagavad Gita · 4.38

न हि ज्ञानेन सदृशं पवित्रमिह विद्यते।तत्स्वयं योगसंसिद्धः कालेनात्मनि विन्दति॥

na hi jñānena sadṛiśhaṁ pavitram iha vidyate tat svayaṁ yoga-saṁsiddhaḥ kālenātmani vindati

In this world, there is nothing as purifying as knowledge. One who has become perfected in yoga discovers that knowledge within the Self, in due course of time.

— Bhagavad Gita 4.38

Source: Sacred-Texts.com (Sanskrit) + Bhagavad-Gita.io (translations)