Sriman Mahaprabhu said,
bahubhir militvā yat kīrtanaṁ tad eva saṅkīrtanam
Congregational chanting is sankirtan, and if we can do sankirtan without offence we must be benefitted. In Kali-yuga the only religion for the conditioned souls is Harinam-sankirtan. We can see this in the scriptures, all over the Vedic literature.
Sriman Mahaprabhu appeared five hundred years ago in Sridham Nabadwip, Mayapur for that yuga-dharma, for spreading Krishna consciousness, in this mundane world. In Chaitanya-charitamrta we can see,
tāhā bilāite prabhura nade āgamana
The religion of the conditioned souls, of all the jiva-souls, in this age of Kali is Harinam-sankirtan. In Srimad Bhagavatam, the gist of all the Vedic scriptures, we can see,
kṛṣṇa-varṇaṁ tviṣākṛṣṇaṁ sāṅgopāṅgāstra-pārṣadam
yajñaiḥ saṅkīrtana-prāyair yajanti hi sumedhasaḥ
(Śrīmad Bhāgavatam: 11.5.32)
In Kali-yuga, Harinam-sankirtan is the only process, and it is a very sweet and very easy process to go to our destiny, Goloka Vrndavan, where we can get service to Lord Krishna. Here we are in the plane of exploitation: everybody is trying to exploit everybody else and this is the nature of this mundane world. But in the transcendental, spiritual, world, all the divine entities are always engaged in service to the Lord. All entities are serving everyone else in favour of Sri Krishna, and they are getting joyfulness, they are getting ecstasy, they are getting love, beauty, charm, and so on. We can see this description in Brahma-samhita.
We can see four ages in this mundane world: Satya, Treta, Dvapara, and Kali. Every age has a religion for rescuing the jiva-souls. We can see in the scriptures that the process is different in every yuga. We can see that there is also a chanting process in every age, but it is different. The Satya-yuga chanting process is:
nārāyaṇa-para vedā nārāyaṇa-parākṣarāḥ
nārāyaṇa-parā muktir nārāyaṇa-parā gatiḥ
rāma nārāyaṇānanta mukunda madhusūdana
kṛṣṇa keśava kaṁsāre hare vaikuṇṭha vāmana
hare murāre madhu-kaiṭabhāre
gopāla govinda mukunda saure
yajñeśa nārāyaṇa kṛṣṇa viṣṇo
virāśrayaṁ māṁ jagadīśa rakṣa
hare kṛṣṇa hare kṛṣṇa kṛṣṇa kṛṣṇa hare hare
hare rāma hare rāma rāma rāma hare hare
This is the process given by Mahaprabhu, Sri Chaitanyadev. Nama-sankirtan was revealed in this mundane world through Sri Chaitanya Mahaprabhu. Kali means the age of quarrel, and we can see all inauspiciousness in Kali-yuga, but one auspicious thing is that,
kaler doṣa-nidhe rājann asti hy eko mahān guṇaḥ
kīrtanād eva kṛṣṇasya mukta-bandhaḥ paraṁ vrajet
(Śrīmad Bhāgavatam: 12.3.51)
Many things are bad—actually we can say that everything is bad in Kali-yuga—and there is no practical religion the jiva-souls can practise. And because of that one topmost facility is given by Krishna, that if we can chant His Name properly, without offence, then we can get liberation from this bad environment and we can establish ourselves in the divine service plane of Goloka Vrndavan where we can exclusively do seva to Sri Sri Radha Govinda.
In other ages we can see that the practising process is very hard.
kṛte yad dhyāyato viṣṇuṁ tretāyāṁ yajato makhaiḥ
dvāpare paricharyāyāṁ kalau tad dhari-kīrtanāt
(Srimad Bhagavatam: 12.3.52)
[“Whatever results were obtained by meditating on the Personality of Lord Vishnu in Satya-yuga, or by performing elaborate sacrifices in Treta-yuga, or by performing Deity worship in Dvapara-yuga, can be obtained in Kali-yuga by simply performing the congregational chanting of the Holy Names of Lord Hari.”]
With so much austerity what result was obtained in the other three yugas, the conditioned souls of this Kali-yuga can get very easily through following this very happy process, and they are getting more than that: liberation, and after liberation, service to Krishna.
harer nāma harer nāma harer nāmaiva kevalam
kalau nāsty eva nāsty eva nāsty eva gatir anyathā
Mahaprabhu said this mahamantram is the only process to get real liberation and entrance to the transcendental service world. Actually we are all the members of that transcendental service world, but unfortunately we came here and are experiencing birth and death, sadness, happiness, and many things here. But it is all anitya, temporary, and our permanent plane is the service plane; that is actually our home. Everyone is serving and getting happiness, joyfulness, ecstasy, nectar, love, beauty, charm, and all fulfilment there in our home and we need to go that place, and the process in Kali-yuga is Harinam-sankirtan. This is the scriptural advice and Mahaprabhu actually manifested it. Punah pravartaka: through Mahaprabhu it was revealed in this mundane world. Then we have no other intention and we have no need to take other facilities from the scriptures: if we can only take that facility, we must be benefitted.
After Sriman Mahaprabhu, his dearmost associates, the six goswamis and others, preached Harinam-sankirtan in this world and in this age it was widely preached by Srila Bhakti Siddhanta Saraswati Thakur. He preached this conception of Harinam-sankirtan all over India, and he tried to preach it all over the world. Today we can see how it has spread all over the world by our divine master Srila A.C. Bhaktivedanta Swami Prabhupad and also our Srila Guru Maharaj, Om Visnupad Srila Bhakti Raksak Sridhar Deva-Goswami. Now all over India, and all over the world, they are getting much peace, joy, and happiness through chanting the Hare Krishna mahamantra. All over the world the conditioned souls are becoming inspired with this mahamantra. We are also a part of that, and we are feeling much happiness.