Bhagavatapurana 8.24.48

8.24.48

yatsevayāgneriva rudrarodanaṃ pumān vijahyān malamātmanastamaḥ /
bhajeta varṇaṃ nijameṣa so 'vyayo bhūyāt sa īśaḥ paramo gurorguruḥ //

48. "May that undecaying Lord, the great Preceptor of our preceptor, be our preceptor by whose worship (by worshipping whom) a person, like a piece of silver blown in fire, can get rid of his darkening impurity and attain to (recover) his own pure colour and nature!