And if we accept the Vedic conclusion as stated in the Bhagavad-gita that these material bodies are perishable in due course of time (antavanta ime dehah) but that the soul is eternal (nityasyoktah saririnah), then we must remember always that the body is like a dress; therefore why lament the changing of a dress? The material body has no factual existence in relation to the eternal soul. It is something like a dream. In a dream we may think of flying in the sky, or sitting on a chariot as a king, but when we wake up we can see that we are neither in the sky nor seated on the chariot. The Vedic wisdom encourages self-realization on the basis of the nonexistence of the material body. Therefore, in either case, whether one believes in the existence of the soul or one does not believe in the existence of the soul, there is no cause for lamentation for loss of the body.
Change of body by the atomic individual soul is an accepted fact. Even the modern scientists who do not believe in the existence of the soul, but at the same time cannot explain the source of energy from the heart, have to accept continuous changes of body which appear from childhood to boyhood and from boyhood to youth and again from youth to old age. From old age, the change is transferred to another body. This has already been explained in a previous verse (2.13).
Transference of the atomic individual soul to another body is made possible by the grace of the Supersoul. The Supersoul fulfills the desire of the atomic soul as one friend fulfills the desire of another. The Vedas, like the Mundaka Upanishad, as well as the Svetasvatara Upanishad, compare the soul and the Supersoul to two friendly birds sitting on the same tree. One of the birds (the individual atomic soul) is eating the fruit of the tree, and the other bird (Krishna) is simply watching His friend. Of these two birds — although they are the same in quality — one is captivated by the fruits of the material tree, while the other is simply witnessing the activities of His friend. Krishna is the witnessing bird, and Arjuna is the eating bird. Although they are friends, one is still the master and the other is the servant. Forgetfulness of this relationship by the atomic soul is the cause of one’s changing his position from one tree to another, or from one body to another. The jiva soul is struggling very hard on the tree of the material body, but as soon as he agrees to accept the other bird as the supreme spiritual master — as Arjuna agreed to do by voluntary surrender unto Krishna for instruction — the subordinate bird immediately becomes free from all lamentations. Both the Mundaka Upanishad (3.1.2) and Svetasvatara Upanishad (4.7) confirm this
This verse is very important for an understanding of how the living entities transmigrate from one body to another. It is explained in the Second Chapter that the living entity is transmigrating from one body to another just as one changes dress. This change of dress is due to his attachment to material existence. As long as he is captivated by this false manifestation, he has to continue transmigrating from one body to another. Due to his desire to lord it over material nature, he is put into such undesirable circumstances. Under the influence of material desire, the entity is born sometimes as a demigod, sometimes as a man, sometimes as a beast, as a bird, as a worm, as an aquatic, as a saintly man, as a bug. This is going on. And in all cases the living entity thinks himself to be the master of his circumstances, yet he is under the influence of material nature