Bhagavad-gītā, which is direct kṛṣṇa-kathā, gives humanity the elementary lesson that the body is perishable and that the consciousness which is spread throughout the body is imperishable. The conscious being, the imperishable self, is eternally existent and cannot be killed under any circumstances, even after the dissolution of the body. Anyone who misunderstands this perishable body to be the self and who works for it in the name of sociology, politics, philanthropy, altruism, nationalism or internationalism, under the false plea of the bodily conception of life, is certainly a fool and does not know the implications of reality and unreality. Some of them are above the modes of ignorance and passion and are situated in the mode of goodness, but mundane goodness is always contaminated by tinges of ignorance and passion. Mundane goodness can enlighten one that the body and the self are different, and one in goodness is concerned with the self and not the body. But due to being contaminated, those in mundane goodness cannot understand the real nature of the self as a person. Their impersonal conception of the self as distinct from the body keeps them in the mode of goodness within material nature, and unless they are attracted by kṛṣṇa-kathā, they will never be liberated from the bondage of material existence. Kṛṣṇa-kathā is the only remedy for all people of the world because it can situate one in pure consciousness of the self and liberate one from material bondage. To preach kṛṣṇa-kathā all over the world, as recommended by Lord Caitanya, is the greatest missionary activity, and all sensible men and women of the world may join in this great movement started by Lord Caitanya.
(Srimad Bhagavatam----3:5:11----purport).

For one who is anxious to engage constantly in hearing such topics, kṛṣṇa-kathā gradually increases his indifference towards all other things. Such constant remembrance of the lotus feet of Lord Kṛṣṇa by the devotee who has achieved transcendental bliss vanquishes all his miseries without delay.
(Srimad Bhagavatam----3:5:13----translation).

We must certainly know that on the absolute plane kṛṣṇa-kathā and Kṛṣṇa are one and the same. The Lord is the Absolute Truth, and therefore His name, form, quality, etc., which are all understood to be kṛṣṇa-kathā, are nondifferent from Him. Bhagavad-gītā, being spoken by the Lord, is as good as the Lord Himself. When a sincere devotee reads Bhagavad-gītā, this is as good as seeing the Lord face to face in his personal presence, but this is not so for the mundane wrangler. All the potencies of the Lord are there when one reads Bhagavad-gītā, provided it is read in the way recommended in the Gītā by the Lord Himself.
(Srimad Bhagavatam----3:5:13----purport).

The impetus for lording it over material nature is the sense of "mine" and "I." "I am the lord of all that I survey. So many things I possess, and I shall possess more and more. Who can be richer than I in wealth and education? I am the master, and I am God. Who else is there but me?" All these ideas reflect the philosophy of ahaṁ mama, the conception that "I am everything." Persons conducted by such a conception of life can never get liberation from material bondage. But even a person perpetually condemned to the miseries of material existence can get relief from bondage if he simply agrees to hear only kṛṣṇa-kathā. In this age of Kali, the process of hearing kṛṣṇa-kathā is the most effective means to gain release from unwanted family affection and thus find permanent freedom in life. The age of Kali is full of sinful reactions, and people are more and more addicted to the qualities of this age, but simply by hearing and chanting of kṛṣṇa-kathā one is sure to go back to Godhead. Therefore, people should be trained to hear only kṛṣṇa-kathā—by all means—in order to get relief from all miseries.
(Srimad Bhagavatam----3:5:44----purport).

The residents of Siddhaloka have full control in the eight kinds of yogic perfection, but from their statement it appears that they are pure devotees. They always merge in the nectarean river of hearing of the pastimes of the Lord. Hearing of the pastimes of the Lord is called kṛṣṇa-kathā. Similarly, there is a statement by Prahlāda Mahārāja that those who are always merged in the ocean of the nectar of describing the Lord's pastimes are liberated and have no fear of the material condition of life.
(Srimad Bhagavatam----4:7:35----purport).