Just like in the spool of your film, there are many pictures. But because you see under certain condition, you see one picture. It is very easy to understand. Actually, the pictures are changing, different pictures, and we are seeing one picture. We are seeing the picture is moving in one picture. Similarly, this body is continuously, every moment, there is different body, different body, different body, every moment, but we are seeing one body. This is our ignorance. But we are changing body. Every moment we are changing body. The spool is going on.
The exact example is that, like that, the film. Every second, changing one picture, one picture, one picture, one picture. And it appears that it is only one picture. One who does not know how the machine, cinematographic machine, is working—the foolish persons—they say, they think that the picture is one and it is moving. No. It is changing. Similarly, the body is also changing. The exact example is changing of dress. Vāsāṁsi jīrṇāni. That is the exact word used in the Bhagavad-gītā.
So even for an ordinary living being, we cannot see how the body is changing, how the living entity is changing from body to another. It is so swiftly, every moment, every second, it is taking place. How you can see? So there is no death; it is simply changing.
So if for ordinary living entity there is no death, how Kṛṣṇa can be appearing and dying? No. Therefore, janma karma me divyaṁ yo jānāti tattvataḥ (BG 4.9). One who knows in truth how Kṛṣṇa is appearing, how Kṛṣṇa is disappearing, he is learned. He is learned in the spiritual science, and for him, as soon as he becomes learned, well versed in the spiritual science, Kṛṣṇa science, he immediately becomes liberated. Caitanya Mahāprabhu confirms, yei kṛṣṇa-tattva-vettā sei guru haya (CC Madhya 8.128). Because one who has understood Kṛṣṇa in truth, he is liberated person. Therefore he is guru.
Guru cannot be a conditioned soul. Guru must be liberated. Because without complete knowledge of Kṛṣṇa, without being free from the contamination of the three modes of material nature . . . one cannot understand Kṛṣṇa on account of his being engrossed with these three material modes of nature. And Kṛṣṇa says, "One who understand Me rightly, he becomes immediately free." Tyaktvā dehaṁ punar janma naiti (BG 4.9). Just like we are changing our dress or our different bodies every moment, so Kṛṣṇa says, tyaktvā deham.