SB 7.5.31
na te viduh svartha-gatim hi visnum
durasaya ye bahir-artha-maninah
andha yathandhair upaniyamanas
te ’pisa-tantryam uru-damni baddhah
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Persons who are strongly entrapped by the consciousness of enjoying material life, and who have therefore accepted as their leader or guru a similar blind man attached to external sense objects, cannot understand that the goal of life is to return home, back to Godhead, and engage in the service of Lord Visnu. As blind men guided by another blind man miss the right path and fall into a ditch, materially attached men led by another materially attached man are bound by the ropes of fruitive labor, which are made of very strong cords, and they continue again and again in materialistic life, suffering the threefold miseries.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Since there must always be a difference of opinion between demons and devotees, Hiranyakasipu, when criticized by his son Prahlada Maharaja, should not have been surprised that Prahlada Maharaja differed from his way of life. Nonetheless, Hiranyakasipu was extremely angry and wanted to rebuke his son for deriding his teacher or spiritual master, who had been born in the brahmana family of the great acarya Sukracarya. The word sukra means “semen,” and acarya refers to a teacher or guru. Hereditary gurus, or spiritual masters, have been accepted everywhere since time immemorial, but Prahlada Maharaja declined to accept such a seminal guru or take instruction from him. An actual guru is srotriya, one who has heard or received perfect knowledge through parampara, the disciplic succession. Therefore Prahlada Maharaja did not recognize a seminal spiritual master. Such spiritual masters are not at all interested in Visnu. Indeed, they are hopeful of material success (bahir-artha-maninah). The word bahih means “external,” artha means “interest,” and manina means “taking very seriously.” Generally speaking, practically everyone is unaware of the spiritual world. The knowledge of the materialists is restricted within the four-billion-mile limit of this material world, which is in the dark portion of the creation; they do not know that beyond the material world is the spiritual world. Unless one is a devotee of the Lord, one cannot understand the existence of the spiritual world. Gurus, teachers, who are simply interested in this material world are described in this verse as andha, blind. Such blind men may lead many other blind followers without true knowledge of material conditions, but they are not accepted by devotees like Prahlada Maharaja. Such blind teachers, being interested in the external, material world, are always bound by the strong ropes of material nature.