SB 5.12.12
rahuganaitat tapasa na yati
na cejyaya nirvapanad grhad va
na cchandasa naiva jalagni-suryair
vina mahat-pada-rajo-’bhisekam
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
My dear King Rahugana, unless one has the opportunity to smear his entire body with the dust of the lotus feet of great devotees, one cannot realize the Absolute Truth. One cannot realize the Absolute Truth simply by observing celibacy [brahmacarya], strictly following the rules and regulations of householder life, leaving home as a vanaprastha, accepting sannyasa, or undergoing severe penances in winter by keeping oneself submerged in water or surrounding oneself in summer by fire and the scorching heat of the sun. There are many other processes to understand the Absolute Truth, but the Absolute Truth is only revealed to one who has attained the mercy of a great devotee.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Actual knowledge of transcendental bliss can be bestowed upon anyone by a pure devotee. Vedesu durlabham adurlabham atma-bhaktau. One cannot attain the perfection of spiritual life simply by following the directions of the Vedas. One has to approach a pure devotee: anyabhilasita-sunyam jñana-karmady-anavrtam. By the grace of such a devotee, one can understand the Absolute Truth, Krsna, and one’s relationship with Him. A materialistic person sometimes thinks that simply by executing pious activities and remaining at home one can understand the Absolute Truth. That is denied in this verse. Nor can one understand the Absolute Truth simply by observing the rules and regulations of brahmacarya (celibacy). One only has to serve the pure devotee. That will help one understand the Absolute Truth without fail.