So then Kṛṣṇa says,
aśraddadhānāḥ puruṣā
dharmasyāsya parantapa
aprāpya māṁ nivartante
mṛtyu-saṁsāra-vartmani
(B.G.9:3)
This is very important. Mṛtyu-saṁsāra. What is this saṁsāra? Saṁsāra means that you take your birth once and live for some time, then you die, then you accept another body, then again live for some time, then you die, then you accept another body, and that body you do not know what kind of body you are going to accept. Tathā dehāntara-prāptiḥ (B.G.2:13). Kṛṣṇa says, dehāntara-prāptiḥ: another..., transfer to another body. But what kind of body, that is not mentioned there. That will depend on your work. You may get the body of a demigod, you may get the body of a dog, you may get the body of a tree, you may get the body of a snake—according to your karma.
(Lecture on Bhagavad-Gita----9:2).

Mṛtyu-saṁsāra means this path of regularly, as we are passing on...
ahany ahani lokāni
gacchanti yama-mandiram
śeṣaḥ sthitam icchanti
kim āścaryam ataḥ param
Yudhiṣṭhira Mahārāja, he was asked, "What is the most wonderful thing in the world?" He replied... He was very learned king. "Yes. The most learned thing, most wonderful thing in the world..." You, you have heard seven wonderful things in the world. So Yudhiṣṭhira Mahārāja said: ahany ahani lokāni gacchanti yama-mandiram. Yama-mandira means "the temple of death." Every minute, every second, we are experiencing that living entities are going to the temple of death, either man, animal, ant, so many. This world is called therefore mṛtyu-loka, "the planet for death." "The planet for death." So Yudhiṣṭhira Mahārāja said, ahany ahani lokāni gacchanti yama-mandiram. Ahani, ahany ahani means daily, every day, every moment. At least every day we see so many death list. If you go to the crematorium ground, you can see.
(Lecture on Bhagavad-Gita----9:2-5).

Two things, that is explained. Aśraddadhānāḥ. What Kṛṣṇa is speaking, the instruction, if we have no faith to believe Him, and if we don't accept it, then the result is that he is losing the chance. He got this human form of life to understand God, but if he is missing this opportunity, then the result will be aprāpya māṁ nivartante. We have come from God. Either you go back to home, back to Godhead, or again we go back to the cycle of birth and death. Mṛtyu-saṁsāra-vartmani. The cycle of birth and death, it is called mṛtyu-saṁsāra. Saṁsāra meanstribulation, tribulation, sufferings. Suffering... The ultimate suffering is mṛtyu, death. So death, again birth. That is also suffering. Although we forget, but to take birth is a great suffering. Great suffering means you have to enter the womb of the mother and you have to grow your body and there is risk of being killed also. Especially at the present moment they are killing the child in the womb. So just imagine how much suffering it is. And if he is killed, if the child is killed, then his term of imprisonment in that body is not finished. Therefore he has to enter again another body, again enter into the mother's womb. And, it may be, many hundreds of years may pass on before he can again see light. So it is great suffering.
(Lecture on Bhagavad-Gita----9:5).

Kṣaṇa-pralaya means when Brahmā's day and night. But there is mahā-pralaya. That will stay we do not know how many millions of years. So this is called millennium. So Nārada Muni remembers this. Therefore he says, ahaṁ purā atīta-bhave. This is called bhava, bhava. Bhava means to come into existence and again finish. Just like this bhava-saṁsāra. It is called bhava-saṁsāra. Bhava-saṁsāra means I have got this body, and it will be finished. Again I shall get another body. Again it will be finished. So where is the science to understand these things? Who can explain? Where is the scientist? Purā atīta-bhave? Is there any scientist? Is there? So what is their knowledge? Very meager knowledge. Two plus two. That's all. (laughs) And they're very much proud. Who can explain this? Purā atīta-bhave. They do not know purā, they do not know atīta, bhave. And abhavam. And "I existed. And I can remember." Is that perfection possible? But this is a fact. It is a fact. One may believe or not believe. They are making research institute, big, big... Yesterday Bon Mahārāja was speaking... What is this research? Research here. And Nārada Muni says that "In my previous life I was like this." Where is, where is the research?
(Lecture on Srimad Bhagavatam----1:5:23).

So generally people are so much ignorant that they cannot understand their miserable condition. This is called saṁsāra. Saṁsāra means entanglement in these miserable conditions of material existence. And bhuñje narakādi duḥkha. By miserable condition we want to compensate this miserable condition. But due to our ignorance we become more and more miserable and, narakādi-duḥkha, the hellish life. Nānā yoni brahman kare, kadarya bhakṣaṇa kare, tāra janma adho pāte yāya. We are circumambulating various types of species of life and eating all sorts of nasty things, and this is the condition of material existence. Narakādi duḥkha. Narakādi duḥkha means hellish condition. But we do not understand. This is our ignorance. Hellish condition.
(Lecture on Sri Caitanya Caritamrta----2:22:11-15).