Bhagavatapurana 7.15.26

7.15.26

yasya sākṣādbhagavati jñānadīpaprade gurau /
martyāsaddhīḥ śrutaṃ tasya sarvaṃ kuñjaraśaucavat //

26. All that is imparted to, and learnt by, any one who improperly regards, as an ordinary mortal, his Guru (Preceptor) who is directly the Almighty Lord and gives him the light of wisdom, is comparable to the cleansing or bath of an elephant.