Srimad Bhagavatam Canto 11, Chapter 17, Text 32

SB 11.17.32

agnau gurav atmani ca
 sarva-bhutesu mam param
aprthag-dhir upasita
 brahma-varcasvy akalmasah
 
Translation: 
 
Thus enlightened in Vedic knowledge by service to the spiritual master, freed from all sins and duality, one should worship Me as the Supersoul, as I appear within fire, the spiritual master, one’s own self and all living entities.
 
Purport: 
 
One becomes glorious and enlightened by faithfully serving a bona fide spiritual master, who is expert in the Vedic way of life. Thus purified, one never engages in sinful activities, which immediately extinguish the fire of spiritual enlightenment; nor does one become foolish and small-minded, trying to exploit material nature for personal sense gratification. A purified human being is aprthag-dhi, or without consciousness of duality, because he has been trained to observe the Supreme Personality of Godhead within all things. Such sublime consciousness should be systematically taught throughout the world so that human society will become peaceful and sublime.
Srimad Bhagavatam Canto 11, Chapter 17, Text 31
Srimad Bhagavatam Canto 11, Chapter 17, Text 33