Bhagavad Gita 4.38

न हि ज्ञानेन सदृशं पवित्रमिह विद्यते |
तत्सस्वयं योगसंसिद्ध: कालेनात्मनि विन्दति

Translation

In this world, there is nothing as purifying as divine knowledge. One who has attained purity of mind through prolonged practice of Yog, receives such knowledge within the heart, in due course of time.