SB 6.7.33
na garhayanti hy arthesu
yavisthanghry-abhivadanam
chandobhyo ’nyatra na brahman
vayo jyaisthyasya karanam
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
The demigods continued: Do not fear criticism for being younger than us. Such etiquette does not apply in regard to Vedic mantras. Except in relationship to Vedic mantras, seniority is determined by age, but one may offer respectful obeisances even to a younger person who is advanced in chanting Vedic mantras. Therefore although you are junior in relationship to us, you may become our priest without hesitation.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
It is said, vrddhatvam vayasa vina: one may be senior without being advanced in age. Even if one is not old, one gains seniority if he is senior in knowledge. Visvarupa was junior in relationship to the demigods because he was their nephew, but the demigods wanted to accept him as their priest, and therefore he would have to accept obeisances from them. The demigods explained that this should not be a cause for hesitation; he could become their priest because he was advanced in Vedic knowledge. Similarly. Canakya Pandita advises, nicad apy uttamam jñanam: one may accept education from a member of a lower social order. The brahmanas, the members of the most elevated varna, are teachers, but a person in a lower family, such as a family of ksatriyas, vaisyas or even sudras, may be accepted as a teacher if he has knowledge. Sri Caitanya Mahaprabhu approved of this when He expressed this opinion before Ramananda Raya (Cc. Madhya 8.128):
kiba vipra, kiba nyasi, sudra kene naya
yei krsna-tattva-vetta, sei ‘guru’ haya
It does not matter whether one is a brahmana, sudra, grhastha or sannyasi. These are all material designations. A spiritually advanced person has nothing to do with such designations. Therefore, if one is advanced in the science of Krsna consciousness, regardless of his position in human society, he may become a spiritual master.