Devotee: Thirteen. "As the embodied soul continually passes in this body from boyhood to youth and then to old age, similarly the soul also passes into another body at death. The self-realized soul is not bewildered by such a change."
Purport: "Since every living entity is an individual soul, each is changing his body at every moment, manifesting sometimes as a child, sometimes as a youth and sometimes as an old man, although the same spirit soul is there and does not undergo any change."
"The individual soul finally changes the body itself in transmigrating from one to another. And since it is sure to have another body in the next birth, either material or spiritual, there was no cause for lamentation by Arjuna on account of death, either over Bhīṣma or over Droṇa, for whom he was so concerned."
Prabhupāda: Now, this simple fact, as it is explained in the Bhagavad-gītā, that dehino 'smin yathā dehe kaumāraṁ yauvanaṁ jarā (BG 2.13), the change of body is taking place every moment. Every moment. Just like this child. The child, if there is some measuring instrument, if you measure this child today, tomorrow you'll find the child has grown, or changed the body. That is a medical science also. The body is changing.
The body is changing, but the soul is there. Just like I had my childhood body, boyhood body, and now I am in a different body, but I remember all the activities of my childhood. Therefore I am permanent and body is changing.
This simple truth, what is the difficulty for the people to understand this simple truth? The body is changing, but I am not changing. I am eternal. Therefore I am not this body. I am not changing. This simple truth, the first instruction of Bhagavad-gītā, the Kṛṣṇa has begun instructing Arjuna . . .
After Arjuna has accepted his discipleship, the first instruction is this, that "You are lamenting on the body of your grandfather and teacher regarding fighting, but your grandfather, or the soul . . ." which is already explained that, "You as soul, I am as the supreme soul, or all these kings and soldiers who have assembled, they are also souls. They existed in the past. Now they have changed their body. Again they will change their body, but they will exist." This is the instruction. The body is changing, and the vivid example? That in this life you are changing body.
So what is the difficulty of understanding this simple truth that the soul is different from the body? And so far eternity of the soul, that is also, there is proof. Because in childhood I was present, in boyhood I was present, in youthhood I was present, and in this old age I am still present.
So naturally it is concluded that when I change this body, I exist.
When I change this body . . . this body will be changed. Tathā dehāntara-prāptiḥ (BG 2.13). As the parents of this child . . . now she is, say, one feet long only. When this child will grow five feet long, the father and mother, will they cry, "Oh, my child! Where is my child, that one-feet long?" He knows. The parents know that, "My child is there, but changed the body." This is a fact. Similarly, "You are lamenting on the body of your grandfather and teacher. Even they change their body, what is the cause of lamentation? They will exist."