When a devotee completely forgets his bodily existence, he should be understood to be liberated. He is no longer encaged in the body. The example is given that when a coconut becomes completely dry, the coconut pulp within the coconut shell separates from the bondage of the shell and the outer covering. By moving the dry coconut, one can hear that the pulp within is no longer attached to the shell or to the covering. Similarly, when one is fully absorbed in devotional service, he is completely disconnected from the two material coverings, the subtle and gross bodies. Dhruva Mahārāja actually attained this stage of life by constantly discharging devotional service. He has already been described as a mahā-bhāgavata, for unless one becomes a mahā-bhāgavata, or a first-class pure devotee, these symptoms are not visible.
(Srimad Bhagavatam----4:12:18----purport).

An important word in this verse is mukta-liṅgaḥ. Mukta means "liberated," and liṅga means "the subtle body." When a man dies, he quits the gross body, but the subtle body of mind, intelligence and ego carries him to a new body. While existing in the present body, the same subtle body carries him from one stage of life to another (for example, from childhood to boyhood) by mental development. The mental condition of a baby is different from that of a boy, the mental condition of a boy is different from that of a young man, and the mental condition of a young man is different from that of an old man. So at death the process of changing bodies takes place due to the subtle body; the mind, intelligence and ego carry the soul from one gross body to another. This is called transmigration of the soul. But there is another stage, when one becomes liberated even from the subtle body; at that time the living entity is competent and fully prepared to be transferred to the transcendental or spiritual world.
(Srimad Bhagavatam----4:12:18----purport).

The description of the bodily symptoms of Śrī Dhruva Mahārāja makes it apparent that he became perfectly fit to be transferred to the spiritual world. One can experience the distinction between the subtle and gross bodies even daily; in a dream, one's gross body is lying on the bed while the subtle body carries the soul, the living entity, to another atmosphere. But because the gross body has to be continued, the subtle body comes back and settles in the present gross body. Therefore one has to become free from the subtle body also. This freedom is known as mukta-liṅga.
(Srimad Bhagavatam----4:12:18----purport).

In Bhagavad-gītā (9.25) it is said, pitṟn yānti pitṛ-vratāḥ. Those who are interested in family welfare are called pitṛ-vratāḥ. There is a planet called Pitṛloka, and the predominating deity of that planet is called Aryamā. He is somewhat of a demigod, and by satisfying him one can help ghostly family members develop a gross body. Those who are very sinful and attached to their family, house, village or country do not receive a gross body made of material elements but remain in a subtle body, composed of mind, ego and intelligence. Those who live in such subtle bodies are called ghosts. This ghostly position is very painful because a ghost has intelligence, mind and ego and wants to enjoy material life, but because he doesn't have a gross material body, he can only create disturbances for want of material satisfaction. It is the duty of family members, especially the son, to offer oblations to the demigod Aryamā or to Lord Viṣṇu.
(Srimad Bhagavatam----4:18:18----purport).

From time immemorial in India the son of a dead man goes to Gayā and, at a Viṣṇu temple there, offers oblations for the benefit of his ghostly father. It is not that everyone's father becomes a ghost, but the oblations of piṇḍa are offered to the lotus feet of Lord Viṣṇu so that if a family member happens to become a ghost, he will be favored with agross body. However, if one is habituated to taking the prasāda of Lord Viṣṇu, there is no chance of his becoming a ghost or anything lower than a human being. In Vedic civilization there is a performance called śrāddha by which food is offered with faith and devotion. If one offers oblations with faith and devotion—either to the lotus feet of Lord Viṣṇu or to His representative in Pitṛloka, Aryamā—one's forefathers will attain material bodies to enjoy whatever material enjoyment is due them. In other words, they do not have to become ghosts.
(Srimad Bhagavatam----4:18:18----purport).

The presence of the Supreme Soul and the individual soul within the body can be perceived by anyone by the fact that as long as the individual soul and the Supersoul are both living within the body, the body is always shining and fresh. But as soon as the Supersoul and the individual soul give up possession of the gross body, it immediately decomposes. One who is spiritually advanced can thus understand the real difference between a dead body and a living body. In conclusion, one should not waste his time by so-called economic development and sense gratification, but should cultivate spiritual knowledge to understand the Supersoul and the individual soul and their relationship. In this way, by advancement of knowledge, one can achieve liberation and the ultimate goal of life. It is said that if one takes to the path of liberation, even rejecting his so-called duties in the material world, he is not a loser at all. But a person who does not take to the path of liberation yet carefully executes economic development and sense gratification loses everything.
(Srimad Bhagavatam----4:22:37----purport).

When the living entity gives up this material body, the vital force still remains intact and is carried to another material body. That is called transmigration, or change of the body, and we have come to know this process as death. Actually, there is no death. The vital force always exists with the soul, and when the soul is awakened from so-called sleep, he can see his eleven friends, or the active senses and the mind with their various desires (wives). The vital life-force remains. Even during our sleeping hours we can understand by virtue of our breathing process that the snake lives by eating the air that passes within this body. Air is exhibited in the form of breathing, and as long as breath is there, one can understand that a sleeping man is alive. Even when the gross body is asleep the vital force remains active and alive to protect the body. Thus the snake is described as living and eating air to keep the body fit for life.
(Srimad Bhagavatam----4:25:35----purport).

When we refer to the body, we include the external gross body with its various limbs, as well as the mind, intelligence and ego. In old age these all become weak when they are attacked by different diseases. The proprietor of the body, the living soul, becomes very sad at not being able to use the field of activities properly. In Bhagavad-gītā it is clearly explained that the living entity is the proprietor of this body (kṣetra jña) and that the body is the field of activities (kṣetra). When a field is overgrown with thorns and weeds, it becomes very difficult for the owner to work it. That is the position of the spirit soul when the body itself becomes a burden due to disease. Extra burdens are placed on the body in the form of anxiety and general deterioration of the bodily functions.
(Srimad Bhagavatam----4:28:5----purport).

The living entity wishes to enjoy the material world in different ways, and therefore by nature's law he is allowed to transmigrate from one body to another, exactly as a person transmigrates from the body of an infant to a child to a boy to a youth to a man. This process is constantly going on. At the last stage, when the gross body becomes old and invalid, the living entity is reluctant to give it up, despite the fact that it is no longer usable. Although material existence and the material body are not comfortable, why does the living entity not want to leave? As soon as one gets a material body, he has to work very hard to maintain it. He may engage in different fields of activity, but whatever the case, everyone has to work very hard to maintain the material body.
(Srimad Bhagavatam----4:28:10----purport).

The living entity is covered by two different types of bodies—the gross body and the subtle body. At death we can see that the gross body is finished, but actually the living entity is carried by the subtle body to another gross body. The so-called scientists of the modern age cannot see how the subtle body is working in carrying the soul from one body to another. This subtle body has been figuratively described as a serpent, or the city's police superintendent. When there is fire everywhere, the police superintendent cannot escape either. When there is security and an absence of fire in the city, the police superintendent can impose his authority upon the citizens, but when there is an all-out attack on the city, he is rendered useless. As the life air was ready to leave the gross body, the subtle body also began to experience pain.
(Srimad Bhagavatam----4:28:13----purport).

It is clear in this verse that at the time of death thoughts of material enjoyment do not go away. This indicates that the living entity, the soul, is carried by the subtle body—mind, intelligence and ego. Due to false ego, the living entity still wants to enjoy the material world, and for want of material enjoyment he becomes sorry or sad. He still makes intellectual plans to further his existence, and therefore, although he gives up the gross body, he is carried by the subtle body to another gross body. The transmigration of the subtle body is never visible to material eyes; therefore when one gives up the gross body, we think that he is finished. Plans for material enjoyment are made by the subtle body, and the gross body is the instrument for enjoying these plans. Thus the gross body can be compared to the wife, for the wife is the agent for all kinds of sense gratification. Because of long association with the gross body, the living entity becomes very sad to be separated from it. The mental activity of the living entity obliges him to accept another gross body and continue his material existence.
The Sanskrit word strī means "expansion." Through the wife one expands his various objects of attraction—sons, daughters, grandsons and so on. Attachment to family members becomes very prominent at the time of death. One often sees that just before leaving his body a man may call for his beloved son to give him charge of his wife and other paraphernalia. He may say, "My dear boy, I am being forced to leave. Please take charge of the family affairs." He speaks in this way, not even knowing his destination.
(Srimad Bhagavatam----4:28:17----purport).

Because of his desire to enjoy the material world, the living entity is dressed with the material gross and subtle bodies. Thus he is given a chance to enjoy the senses. The senses are therefore the instruments for enjoying the material world; consequently the senses have been described as friends. Sometimes, because of too much sinful activity, the living entity does not get a material gross body, but hovers on the subtle platform. This is called ghostly life. Because of his not possessing a gross body, he creates a great deal of trouble in his subtle body. Thus the presence of a ghost is horrible for those who are living in the gross body.
(Srimad Bhagavatam----4:29:6----purport).

The living entity has two kinds of body—the subtle body and the gross body. Actually he enjoys through the subtle body, which is composed of mind, intelligence and ego. The gross body is the instrumental outer covering. When the gross body is lost, or when it dies, the root of the gross body—the mind, intelligence and ego—continues and brings about another gross body. Although the gross bodies apparently change, the real root of the gross body—the subtle body of mind, intelligence and ego—is always there. The subtle body's activities—be they pious or impious—create another situation for the living entity to enjoy or suffer in the next gross body. Thus the subtle body continues whereas the gross bodies change one after another.
(Srimad Bhagavatam----4:29:60----purport).

Since modern scientists and philosophers are too materialistic, and since their knowledge is taken away by the illusory energy, they cannot explain how the gross body is changing. The materialistic philosopher Darwin has tried to study the changes of the gross body, but because he had no knowledge of either the subtle body or the soul, he could not clearly explain how the evolutionary process is going on. One may change the gross body, but he works in the subtle body. People cannot understand the activities of the subtle body, and consequently they are bewildered as to how the actions of one gross body affect another gross body.
(Srimad Bhagavatam----4:29:60----purport).

Although the root of distress and happiness is the mind, intelligence and ego, a gross body is still required as an instrument for enjoyment. The gross body may change, but the subtle body continues to act. Unless the living entity gets another gross body, he will have to continue in a subtle body, or a ghostly body. One becomes a ghost when the subtle body acts without the help of the instrumental gross body. As stated in this verse, śayānam imam utsṛjya śvasantam. The gross body may lie on a bed and rest, and even though the machinery of the gross body is working, the living entity may leave, go into a dream, and return to the gross body. When he returns to the body, he forgets his dream. Similarly, when the living entity takes on another gross body, he forgets the present gross body. The conclusion is that the subtle body—mind, intelligence and ego—creates an atmosphere with desires and ambitions that the living entity enjoys in the subtle body. Actually the living entity is in the subtle body, even though the gross body apparently changes and even though he inhabits the gross body on various planets. All the activities performed by the living entity in the subtle body are called illusory because they are not permanent. Liberation means getting out of the clutches of the subtle body. Liberation from the gross body simply involves the transmigration of the soul from one gross body to another. When the mind is educated in Kṛṣṇa consciousness, or higher consciousness in the mode of goodness, one is transferred either to the upper, heavenly planets or to the spiritual world, the Vaikuṇṭha planets. One therefore has to change his consciousness by cultivating knowledge received from Vedic instructions from the Supreme Personality of Godhead through the disciplic succession. If we train the subtle body in this life by always thinking about Kṛṣṇa, we will transfer to Kṛṣṇaloka after leaving the gross body. This is confirmed by the Supreme Personality of Godhead.
(Srimad Bhagavatam----4:29:61----purport).