Saṅkīrtana means chanting of the holy name of the Lord. The Hare Kṛṣṇa movement is not a new movement as people sometimes mistakenly think. The Hare Kṛṣṇa movement is present in every millennium of Lord Brahmā's life, and the holy name is chanted in all the higher planetary systems, including Brahmaloka and Candraloka, not to speak of Gandharvaloka and Apsaroloka. The saṅkīrtana movement that was started in this world five hundred years ago by Śrī Caitanya Mahāprabhu is therefore not a new movement. Sometimes, because of our bad luck, this movement is stopped, but Śrī Caitanya Mahāprabhu and His servants again start the movement for the benefit of the entire world or, indeed, the entire universe.
(Srimad Bhagavatam--7:15:71--purport).

As far as the approved method is concerned, it is enjoined in the śāstras that intelligent men in this age will take to the saṅkīrtana movement, and by so doing they shall worship the Supreme Personality of Godhead Lord Caitanya, whose bodily complexion is golden and who is always accompanied by His confidential devotees to preach this Kṛṣṇa consciousness movement all over the world.
(Srimad Bhagavatam--4:18:8--purport).

The atmosphere created by this saṅkīrtana movement lives in their hearts, and while sleeping they also dream of the singing and glorification of the Lord. In such a way, perfection of Kṛṣṇa consciousness can be attained.
(Srimad Bhagavatam--3:22:33--purport).

According to one's development in consciousness, one realizes his spiritual identity, and thus when one's existential position is purified fully, he becomes situated in brahmānanda, which is ultimately unlimited. Therefore the saṅkīrtana movement contributed by the Supreme Personality of Godhead as Lord Caitanya is the direct and easiest process for coming to the purest form of consciousness—Kṛṣṇa consciousness, the platform on which the Supreme Personality is fully realized.
(Srimad Bhagavatam--4:21:35--purport).

To chant the holy name and dance in ecstasy is so easy and sublime that one can achieve all the benefits of spiritual life simply by following this process. Therefore Śrī Caitanya Mahāprabhu declares, paraṁ vijayate śrī-kṛṣṇa-saṅkīrtanam: "All glories to Śrī Kṛṣṇa saṅkīrtana!" The saṅkīrtana movement we have started offers the best process for becoming purified of all sinful reactions and coming immediately to the platform of spiritual life.
(Srimad Bhagavatam--6:2:11--purport).

In Kali-yuga, intelligent men worship the Supreme Personality of Godhead in the form of Śrī Caitanya Mahāprabhu, who is always accompanied by His associates such as Nityānanda, Advaita, Gadādhara and Śrīvāsa. The entire Kṛṣṇa consciousness movement is based on the principles of the saṅkīrtana movement inaugurated by Śrī Caitanya Mahāprabhu. Therefore one who tries to understand the Supreme Personality of Godhead through the medium of the saṅkīrtana movement knows everything perfectly. He is sumedhas, a person with substantial intelligence.
(Srimad Bhagavatam--7:9:38--purport).

Śrī Caitanya Mahāprabhu set a practical example in that He did not establish any temples or Deities, but He profusely introduced the saṅkīrtana movement. Therefore Kṛṣṇa consciousness preachers should give more stress to the saṅkīrtana movement, especially by distributing transcendental literature more and more. This helps the saṅkīrtana movement. Whenever there is a possibility to worship the Deity, we may establish many centers, but generally we should give more stress to the distribution of transcendental literature, for this will be more effective in converting people to Kṛṣṇa consciousness.
(Srimad Bhagavatam--7:14:39--purport).

When Śrī Caitanya Mahāprabhu appeared, He ushered in the era for the saṅkīrtana movement. It is also said that for ten thousand years this era will continue. This means that simply by accepting the saṅkīrtana movement and chanting the Hare Kṛṣṇa mahā-mantra, the fallen souls of this Kali-yuga will be delivered. After the Battle of Kurukṣetra, at which Bhagavad-gītā was spoken, Kali-yuga continues for 432,000 years, of which only 5,000 years have passed. Thus there is still a balance of 427,000 years to come. Of these 427,000 years, the 10,000 years of the saṅkīrtana movement inaugurated by Śrī Caitanya Mahāprabhu 500 years ago provide the opportunity for the fallen souls of Kali-yuga to take to the Kṛṣṇa consciousness movement, chant the Hare Kṛṣṇa mahā-mantra and thus be delivered from the clutches of material existence and return home, back to Godhead.
(Srimad Bhagavatam--8:5:23).

The Śrīmad-Bhāgavatam and Bhagavad-gītā give definite directions on how to stop the struggle for existence and how to survive in eternal life. Thesaṅkīrtana movement, therefore, is a great opportunity. Simply by hearing Bhagavad-gītā and chanting the Hare Kṛṣṇa mahā-mantra, one becomes completely purified. Thus the struggle for existence ceases, and one goes back home, back to Godhead.
(Srimad Bhagavatam--8:5:23--purport).