In this verse, the word dvija-deva-mantram is very important. The word mantra means “that which delivers one from the material world.” Only the dvijas (the brāhmaṇas) and the devas (the demigods) can be delivered from material existence by the instructions of the Supreme Personality of Godhead. Whatever is spoken by the Supreme Personality of Godhead is a mantra and is suitable for delivering the conditioned souls from mental speculation. The conditioned souls are engaged in a struggle for existence (manaḥ ṣaṣṭhānīndriyāṇi prakṛti-sthāni karṣati). Deliverance from this struggle constitutes the highest benefit, but unless one gets a mantra from the Supreme Personality of Godhead, deliverance is impossible. The beginning mantra is the Gāyatrī mantra. Therefore, after purification, when one is qualified to become a brāhmaṇa (dvija), he is offered the Gāyatrī mantra. Simply by chanting the Gāyatrī mantra, one can be delivered. This mantra, however, is suitable only for the brāhmaṇas and demigods. In Kali-yuga, we are all in a very difficult position, in which we need a suitable mantra that can deliver us from the dangers of this age. Therefore the Supreme Personality of Godhead, in His incarnation as Lord Caitanya, gives us the Hare Kṛṣṇa mantra.

harer nāma harer nāma
 harer nāmaiva kevalam
kalau nāsty eva nāsty eva
 nāsty eva gatir anyathā

“In this age of quarrel and hypocrisy the only means of deliverance is chanting the holy name of the Lord. There is no other way. There is no other way. There is no other way.” In His Śikṣāṣṭaka, Lord Caitanya says, paraṁ vijayate śrī-kṛṣṇa-saṅkīrtanam: “All glories to the chanting of śrī-kṛṣṇa-saṅkīrtana!” The mahā-mantra — Hare Kṛṣṇa, Hare Kṛṣṇa, Kṛṣṇa Kṛṣṇa, Hare Hare/ Hare Rāma, Hare Rāma, Rāma Rāma, Hare Hare — is directly chanted by the Lord Himself, who gives us this mantra for deliverance.

We cannot invent any means to be delivered from the dangers of material existence. Here, even the demigods, such as Lord Brahmā and Lord Śiva, and the prajāpatis, such as Dakṣa, are said to be like illuminating sparks in the presence of the Supreme Lord, who is compared to a great fire. Sparks are beautiful as long as they are in the fire. Similarly, we have to remain in the association of the Supreme Personality of Godhead and always engage in devotional service, for then we shall always be brilliant and illuminating. As soon as we fall from the service of the Lord, our brilliance and illumination will immediately be extinguished, or at least stopped for some time. When we living entities, who are like sparks of the original fire, the Supreme Lord, fall into a material condition, we must take the mantra from the Supreme Personality of Godhead as it is offered by Śrī Caitanya Mahāprabhu. By chanting this Hare Kṛṣṇa mantra, we shall be delivered from all the difficulties of this material world.