Srimad Bhagavatam Canto 11, Chapter 18, Text 39

SB 11.18.39

tavat paricared bhaktah
 sraddhavan anasuyakah
yavad brahma vijaniyan
 mam eva gurum adrtah
Until a devotee has clearly realized spiritual knowledge, he should continue with great faith and respect and without envy to render personal service to the guru, who is nondifferent from Me.
As stated by Srila Visvanatha Cakravarti Thakura in his Gurv-astaka prayers, yasya prasadad bhagavat-prasadah: one receives the mercy of the Supreme Lord through the mercy of the bona fide spiritual master. A devotee who has been blessed by his guru with spiritual knowledge becomes qualified to directly engage in the mission of the Supreme Personality of Godhead. Srila Prabhupada always emphasized that service to the spiritual master in separation, pushing on the mission of the guru, is the highest form of devotional service. The word paricaret in this verse indicates waiting upon one’s master by rendering personal service. In other words, one who has not clearly realized the teachings of his spiritual master should remain very close to the guru to avoid falling down into illusion, but one who has acquired realized knowledge by the mercy of his spiritual master may expand the spiritual master’s mission by traveling around the world to preach Krsna consciousness.
Srimad Bhagavatam Canto 11, Chapter 18, Text 38
Srimad Bhagavatam Canto 11, Chapter 18, Text 40-41