This is a verse from Śrīmad-Bhāgavatam (SB 11.17.27) spoken by Lord Kṛṣṇa when He was questioned by Uddhava regarding the four social and spiritual orders of society. The Lord was specifically instructing how a brahmacārī should behave under the care of a spiritual master. A spiritual master is not an enjoyer of facilities offered by his disciples. He is like a parent. Without the attentive service of his parents, a child cannot grow to manhood; similarly, without the care of the spiritual master one cannot rise to the plane of transcendental service.
The spiritual master is also called ācārya, or a transcendental professor of spiritual science. The Manu-saṁhitā (2.140) explains the duties of an ācārya, describing that a bona fide spiritual master accepts charge of disciples, teaches them the Vedic knowledge with all its intricacies, and gives them their second birth. The ceremony performed to initiate a disciple into the study of spiritual science is called upanīti, or the function that brings one nearer to the spiritual master. One who cannot be brought nearer to a spiritual master cannot have a sacred thread, and thus he is indicated to be a śūdra. The sacred thread on the body of a brāhmaṇa, kṣatriya or vaiśya is a symbol of initiation by the spiritual master; it is worth nothing if worn merely to boast of high parentage. The duty of the spiritual master is to initiate a disciple with the sacred thread ceremony, and after this saṁskāra, or purificatory process, the spiritual master actually begins to teach the disciple about the Vedas. A person born a śūdra is not barred from such spiritual initiation, provided he is approved by the spiritual master, who is duly authorized to award a disciple the right to be a brāhmaṇa if he finds him perfectly qualified. In the Vāyu Purāṇa an ācārya is defined as one who knows the import of all Vedic literatures, abides by their rules and regulations, and teaches his disciples to act in the same way.
Only out of His immense compassion does the Personality of Godhead reveal Himself as the spiritual master. Therefore in the dealings of an ācārya there are no activities but those of transcendental loving service to the Lord. He is the Supreme Personality of Servitor Godhead. It is worthwhile to take shelter of such a steady devotee, who is called āśraya-vigraha, or the manifestation or form of the Lord of whom one must take shelter.