This process of true initiation (diksa) is also confirmed in the Bhagavad-gītā:

“Just try to learn the truth by approaching a spiritual master. Inquire from him submissively and render service unto him. The self-realized soul can impart knowledge unto you because he has seen the truth.” (Bhagavad-gita, 4:34 [original 1972 edition])

COMMENT IHKM:

In this verse ( Bg 4:34), the word “upadeksyanti” is translated literally as “initiate”; however, in the full translation, this “initiate” is rendered to mean that the guru must “impart knowledge”. Consequently, the “Prabhupada is siksa and not diksa guru” proponents are caught in a logical trap that they themselves have set. If Srila Prabhupada is capable of imparting “knowledge” or “divya-jnana” to neophytes, which the GBC concedes by endorsing him as the preeminent siksa guru for ISKCON, then by definition he must also be capable of giving or initiating (initiating) diksa. Transmission of transcendental knowledge (transcendental siksa) is, after all, the main component of diksa:

“Dīkṣā actually means initiating a disciple with transcendental knowledge by which he becomes freed from all material contamination. (Madhya-lila, 4.111, purport)

“Dīkṣā is the process by which one can awaken his transcendental knowledge and vanquish all reactions caused by sinful activity. A person expert in the study of the revealed scriptures knows this process as dīkṣā.” The regulative principles of dīkṣā are explained in the Hari-bhakti-vilāsa (2.3,4) and in Bhakti-sandarbha (283). (C.C. Mad., 15.108, purport)

In other words, the spiritual master awakens the sleeping living entity to his original consciousness so that he can worship Lord Viṣṇu. This is the purpose of dīkṣā, or initiation. Initiation means receiving the pure knowledge of spiritual consciousness. (C.C. Mad., 9.61, purport)

The spiritual master, by his words, can penetrate into the heart of the suffering person and inject knowledge transcendental, which alone can extinguish the fire of material existence. (S.B. 1.7.22, purport)

Devotee: Srila Prabhupada when you’re not present with us , how is it possible to receive instructions? For example in questions that may arise…

Srila Prabhupada: Well the questions are answ… answers are there in my books.
(Morning Walk, Los Angeles, 13/5/73)

“In my books the philosophy of Krishna Consciousness is explained fully so if there is anything which you do not understand, then you simply have to read again and again. By reading daily the knowledge will be revealed to you and by this process your spiritual life will develop.” Letter — Bombay 22 November, 1974

“Every one of you must regularly read our books at least twice, in the morning and evening, and automatically all questions will be answered. So utilise whatever time you find to make a thorough study of my books. Then all your questions will be answered” (Letter to Randhira, 24/01/70 and Upendra 7/1/76)

“If there is no chance to serve the spiritual master directly, a devotee should serve him by remembering his instructions. There is no difference between the spiritual master’s instructions and the spiritual master himself. In his absence, therefore, his words of direction should be the pride of the disciple.” (CC Adi 1.35 : purport)

“The eternal bond between disciple and spiritual master begins from the first day he hears.” (SP Letter to Jadurani, 4/9/72)

“Why distinguish between chanting and book distribution? These books I have recorded and chanted, and they are transcribed. It is spoken kirtanas. So book distribution is also chanting. These are not ordinary books. It is recorded chanting. Anyone who reads, he is hearing.” (Letter to Rupanuga Das, 19/10/74)

Srila Prabhupada: “Even a moment’s association with a pure devotee—all success.”
Revatīnandana: Does that also apply to reading the words of a pure devotee?
Prabhupāda: Yes.
Revatīnandana: Even a little association with your books has the same effect?
Prabhupāda: Effect, of course, it requires both the things. One must be very eager to take it.
(SP-Room-Conversation, 13/12/70)

Paramahaṁsa: My question is: A pure devotee, when he comments Bhagavad-gītā, someone who never sees him physically, but he just comes in contact with his commentary, explanation, is this the same thing?

Prabhupāda: Yes. You can associate with Kṛṣṇa by reading Bhagavad-gītā. And these saintly persons, they have given their explanations, comments. So where is the difficulty? Everyone is helping you. (SP Morning-walk, Paris 11/6/74)

If death takes place, let it take here. So there is nothing to be said new. Whatever I have to speak, I have spoken in my books. Now you try to understand it and continue your endeavor. Whether I am present or not present, it doesn’t matter. (770517ar.vrn Conversations)

If I depart there is no cause for lamentation. I will always be with you through my books and orders. I will always remain with you in that way. (BTG 13:1-2, December 1977)

COMMENT IHKM:

Here is a statement by a self-proclaimed ISKCON “guru” (Sivarama) that is totally inconsistent with Srila Prabhupada’s philosophy:

Sivarama says: “Srila Prabhupada has taught us that the disciplic succession is a living affair […] The law of disciplic succession is that one approaches a living spiritual master – living in the sense of being physically present.” (Sivarama Swami ISKCON Journal, p.31, GBC 1990)

A pure concoction of Sivarama. It is hard to reconcile the above assertion with statements such as:

“Physical presence is not important.”
(Srila Prabhupada Room conversation, 6/10/77, Vrindavan)
or
“Physical presence is immaterial.”
(Srila Prabhupada Letter, 19/1/67)

Of course, we must have a guru who is external, since in the conditioned stage pure reliance on the Supersoul is not possible, but nowhere does Srila Prabhupada teach that this physical guru must also be physically present:

“Therefore one must take advantage of the vani, not the physical presence.”
(C.c. Antya, concluding words)

Srila Prabhupada practically demonstrated this principle by initiating large numbers of his disciples without ever meeting them physically at all. This fact in itself proves that diksa can be obtained without any physical involvement from the guru. There is nothing in sastra, or from Srila Prabhupada, linking diksa with physical presence.

75-11-04 Letter: Suci
You have rightly said that the best way to associate with the spiritual master is to follow his instructions. There are two ways of associating, by vani and by vapu. Vani means words and vapu means physical presence. PHYSICAL PRESENCE IS SOMETIMES APPRECIABLE AND SOMETIMES NOT. THEREFORE WE SHOULD TAKE ADVANTAGE OF THE VANI, NOT THE PHYSICAL PRESENCE, BECAUSE THE VANI CONTINUES TO EXIST ETERNALLY. Bhagavad-gita for example is the vani of Lord Krishna. Although Krishna was personally present 5,000 years ago and is no longer present physically from the materialistic viewpoint, still Bhagavad-gita continues. So you have correctly concluded.

SO ALTHOUGH A PHYSICAL BODY IS NOT PRESENT, THE VIBRATION SHOULD BE ACCEPTED AS THE PRESENCE OF THE SPIRITUAL MASTER, VIBRATION. WHAT WE HAVE HEARD FROM THE SPIRITUAL MASTER, THAT IS LIVING.

“He lives forever by his divine instructions, and the follower lives with him.” (S.B. Preface)

More here:
http://prabhupadanugas.blogspot.com/2012/07/the-naked-truth-about-iskcon-guru.html
http://www.harekrsna.de/reform/e_pr_fo.htm