A mantra is a sound vibration that delivers the mind from illusion. When a person chants a mantra consisting of the Lord's names, his mind is freed of distress and he comes to the state of transcendental peace in God consciousness. Of all such mantras, however, the one King Kulaśekhara recommends is a kṛṣṇa-mantra—in other words, one composed of Kṛṣṇa's names. One of these is the Hare Kṛṣṇa mahā-mantra, which Lord Caitanya chanted and which the Upaniṣads proclaim the best mantra for Kali-yuga:
hare kṛṣṇa hare kṛṣṇa kṛṣṇa kṛṣṇa hare hare
hare rāma hare rāma rāma rāma hare hare
iti ṣoḍaśakaṁ nāmnāṁ kali-kalmaṣa-nāśanam
nātaḥ parataropāyaḥ sarva-vedeṣu dṛśyate
"Hare Kṛṣṇa, Hare Kṛṣṇa, Kṛṣṇa Kṛṣṇa, Hare Hare/ Hare Rāma, Hare Rāma, Rāma Rāma, Hare Hare. These sixteen names composed of thirty-two syllables are the only means of counteracting the evil effects of the Kali-yuga. After searching through all the Vedic literature, one cannot find a method of religion for this age so sublime as the chanting of the Hare Kṛṣṇa mantra" (Kali-santaraṇa Upaniṣad).
King Kulaśekhara declares that the kṛṣṇa-mantra destroys one's enemies. We find one confirmation of this in the story of Ajāmila, who chanted the name Nārāyaṇa and was protected from the agents of death. Elsewhere the Śrīmad-Bhāgavatam states,
āpannaḥ saṁsṛtiṁ ghorāṁ yan-nāma vivaśo gṛṇan
tataḥ sadyo vimucyeta yad bibheti svayaṁ bhayam
"Living beings who are entangled in the complicated meshes of birth and death can be freed immediately by even unconsciously chanting the holy name of Kṛṣṇa, which is feared by fear personified" (SB 1.1.14). Also, chanting the holy name of Kṛṣṇa destroys the six mental enemies: lust, anger, greed, illusion, madness, and envy.
Next Kulaśekhara says that the kṛṣṇa-mantra is worshiped throughout the Upaniṣads. For the most part, the Upaniṣads describe the personal form of the Lord indirectly, yet they always point toward Kṛṣṇa. Śrīla Rūpa Gosvāmī reveals this inner meaning of the Upaniṣads in his Nāmāṣṭaka (1):
ayi mukta-kulair upāsyamānāṁ
paritas tvāṁ hari-nāma saṁśrayāmi
"O Hari-nāma! The tips of the toes of Your lotus feet are constantly being worshiped by the glowing radiance emanating from the string of gems known as the Upaniṣads, the crown jewels of all the Vedas. You are eternally adored by liberated souls such as Nārada and Śukadeva. O Hari-nāma! I take complete shelter of You."
The kṛṣṇa-mantra also uproots saṁsāra. Lord Caitanya confirms this in His Śikṣāṣṭaka (1), where He states, bhava-mahā-dāvāgni-nirvāpanam: "The congregational chanting of the Hare Kṛṣṇa mantra extinguishes the blazing fire of repeated birth and death." The kṛṣṇa-mantra is also most effective for driving away the darkness of ignorance. As Lord Caitanya says in the same verse, vidyā-vadhū-jīvanam: "Chanting Hare Kṛṣṇa is the life and soul of transcendental knowledge." Also, the second verse of the Caitanya-caritāmṛta compares Lord Caitanya and Lord Nityānanda, the foremost propagators of the chanting of Kṛṣṇa's names, to the sun and moon: "They have arisen simultaneously on the horizon of Gauḍa [Bengal] to dissipate the darkness of ignorance and thus wonderfully bestow benediction upon all." Elaborating on this point, Śrīla Kṛṣṇadāsa Kavirāja informs us that the material sun and moon are able to dissipate the darkness of the external world, "but these two brothers [Lord Caitanya and Lord Nityānanda] dissipate the darkness of the inner core of the heart and thus help one to meet the two kinds of bhāgavatas [persons or things related to the Supreme Personality of Godhead]" (Cc. Ādi 1.98).
King Kulaśekhara glorifies the kṛṣṇa-mantra as the bestower of infinite opulence. The most valuable thing, even more valuable than the cintāmaṇi stone of this world, is love of Godhead. "Simply chanting the Hare Kṛṣṇa mahā-mantra without offenses vanquishes all sinful activity. Thus pure devotional service, which is the cause of love of Godhead, becomes manifest" (Cc. Ādi 8.26).
King Kulaśekhara also praises the kṛṣṇa-mantra as a type of medicine that relieves the suffering of those who have been bitten by the snake of material distress. In Śrīla Bhaktivinoda Ṭhākura's song Aruṇodaya-kīrtana, Lord Caitanya says to the people of the world, "I have brought the medicine for destroying the illusion of Māyā. Now pray for this hari-nāma mahā-mantra and take it."