Srila Prabhupada Morning Walk, June 9, 1976, Los Angeles, California

Perfect devotee is transferred to spiritual world.
Srila Prabhupada defines moksha, liberation.
Srila Prabhupada explains how the spiritual world is never annihilated.

Srila Prabhupada: Birth and death you stop as soon as you give up this material body. Material body, the birth question comes of the material body. And death also material body. Therefore it is clearly said in the Bhagavad-gita, na jayate na mriyate va.

Indian man: Yes, you are trying to do sadhanas to see what...
Srila Prabhupada: First of all, understand this, that the soul is never born, never dies. But we are seeing birth and death. What is that birth and death? It is of the body. But you are different from the body.
Indian man: Yes, I am different. My soul is different, the atma different from the body. That is the conclusion.
Srila Prabhupada: Birth and death applies to the body. Not to the soul.
Indian man: Yes. That, your karmas, you enjoy and suffer according to your karma.
Srila Prabhupada: That is body, all body.
Indian man: That is body. How long you are going to do that?
Srila Prabhupada: So long you are not a devotee.
Indian man: I mean even if I am a devotee, I go on doing some sins...
Srila Prabhupada: You become devotee, then immediately transfer to the nitya-yukta upasate.
Indian man: Yes, I become a devotee, a true devotee...
Srila Prabhupada:

When you become a perfect devotee then you are transferred to the eternal world and your engagement is upasana eternally.

Indian man: The eternal world. What is that eternal world?
Srila Prabhupada: That you do not know? You read, study? Have you studied Bhagavad-Gita? Do you know that there is an eternal world? There is an eternal world? Do you know that?
Indian man: Our sastras say eternal world...
Srila Prabhupada: Then why do you...?
Indian man: Man is eternal world by going and enjoying there in moksa there.
Srila Prabhupada: So that is moksa.

When you go to the eternal world, that is moksa. That is moksa.

Indian man: Do you separate the eternal world from the Paramatma? It is something, a world like our material world that we have got, physical world that we have got, is going to be out of, the eternal world?
Srila Prabhupada: Yes. Yes. Paras tasmat tu bhavo 'nyo 'vyakto 'vyaktat sanatana [Bg. 8.20]. This word is used, sanatana. Sanatana means eternal. There is another world. Paras tasmat tu bhavo 'nyo 'vyakto 'vyaktat sanatana [Bg. 8.20]. Find out this verse. Everything is there. Devotee: We have to start packing up now. It's quarter past six. We have to leave in ten minutes.
Srila Prabhupada: So now we have to stop. We have to leave. You just refer that verse. Devotee: paras tasmat tu bhavo 'nyo 'vyakto 'vyaktat sanatanah /yah sa sarvesu bhütesu nasyatsu na vinasyati [Bg. 8.20]
Srila Prabhupada: Na vinasyati. The material world will be finished and that will remain.
Devotee: "Yet there is another nature which is eternal and is transcendental to this manifested and unmanifested matter. It is supreme and is never annihilated. When all in this world is annihilated, that part remains as it is."
Srila Prabhupada: That is sanatana. Devotee: "Krsna's superior spiritual energy is transcendental and eternal. It is beyond all the changes of material nature, which is manifest and annihilated during the days and nights of Brahma. Krsna's superior energy is completely opposite in quality to material nature. Superior and inferior nature are explained in the Seventh Chapter." And the next verse?
Srila Prabhupada: No, that's all right.

There is an eternal world, sanatana. That is never annihilated. So when you go to that sanatana-dhama, God is there, sanatana, and there you live eternally and go on rendering service to God. That is (indistinct). There is no question of oneness. The variety is there, but there the varieties are eternal, here the varieties are temporary. That is difference. Everything is there.

Srila Prabhupada Room Conversation, August 25, 1976, Hyderabad, India

Srila Prabhupada explains the spiritual world is full of cows.

Guest (2): What exists between the planet Gokula and the (indistinct) Krsna? Srila Prabhupada: There is a planet who is full of cows, Gokula. That's it. Surabhir abhipalayantam. Cintamani-prakara-sadmasu kalpa-vrksa-laksavrtesu surabhir abhipalayantam [Bs. 5.29]. Krsna is engaged there in tending cows, surabhi cows. That is Gokula. That planet is full of cows. Srila Prabhupada morning walk, December 5, 1976, Hyderabad, India

Srila Prabhupada explains that the Gopis are the highest devotees in the spiritual world.

Devotee: Srila Prabhupada, two boys are here. They are from Caracas. This one boy is Ramanujacarya. He distributed over three thousand Bhagavatams in the month of December. He did over a hundred books every day. (devotees exclaim)
Srila Prabhupada: Wonderful. Thank you very much.
Devotee: This is him, this boy.
Srila Prabhupada: Oh. Very good. The more you distribute books, the more you are blessed. There is no more or less. Everyone is blessed... (laughter) There is no such discrimination, but still, there is some competition. (laughter) In Vrndavana there is no discrimination that gopis are the highest and others... No. Every one is all right. Still, from neutral point of view, the gopis are the highest. Caitanya Mahaprabhu..., ramya kascid upasana vraja-vadhu vargabhir ya kalpita,(?) that "There is no standard of worship, what was conceived by the gopis." Caitanya Mahaprabhu said. There is no distinction between the cowherd boys and the gopis or the trees and the flowers and the calves and cows. It is the absolute platform. But still, in the spiritual world also there is distinction between living entities. That is variety, spiritual variety, visesavada. Srila Prabhupada evening darsana,

February 25, 1977, Mayapura, India