Vedic References on the Hare Krishna Maha-mantra

The Hare Krishna maha-mantra is mentioned in various scriptures as the only means of deliverance in this age of Kali:
 
Kali-santarana Upanishad:
"After searching through all the Vedic literature, one cannot find a method of religion more sublime for this age than the chanting of Hare Krishna.”
– For a discussion of this verse, see Chaitanya Charitamrita, Adi-lila 3.40, Purport
 
Brihan-naradiya Purana:
"For spiritual progress in this Age of Kali, there is no alternative, there is no alternative, there is no alternative to the holy name, the holy name, the holy name of the Lord."
– For a discussion of this verse, see Chaitanya Charitamrita, Adi-lila 7.76, Purport
 
Narada-pancharatra:
“The essence of all Vedic knowledge—comprehending the three kinds of Vedic activity [karma-kanda, jñana-kanda and upasana-kanda], the chandas, or Vedic hymns, and the processes for satisfying the demigods—is included in the eight syllables Hare Krishna, Hare Krishna. This is the reality of all Vedanta. The chanting of the holy name is the only means to cross the ocean of nescience.”
– For a discussion of this verse, see Chaitanya Charitamrita, Adi-lila, 7.76, Purport
 
Narayana-samhita:
“In Dvapara-yuga one could satisfy Krishna or Vishnu only by worshiping Him gorgeously according to the pañcaratrikisystem (temple Deity worship), but in the Age of Kali one can satisfy and worship the Supreme Personality of Godhead Hari simply by chanting the holy name.”
– For a discussion of this verse, see Chaitanya Charitamrita, Adi-lila 7.76, Purport
 
Srimad-Bhagavatam, 12.3.51:
"My dear King, although Kali-yuga is an ocean of faults, there is still one good quality about this age: Simply by chanting the Hare Krishna maha-mantra, one can become free from material bondage and be promoted to the transcendental kingdom."
 
Padma Purana:
"The holy name of Krishna is transcendentally blissful. It bestows all spiritual benedictions, for it is Krishna Himself, the reservoir of all pleasure. Krishna’s name is complete, and it is the form of all transcendental mellows. It is not a material name under any condition, and it is no less powerful than Krishna Himself. Since Krishna’s name is not contaminated by the material qualities, there is no question of its being involved with maya. Krishna’s name is always liberated and spiritual; it is never conditioned by the laws of material nature. This is because the name of Krishna and Krishna Himself are identical."
– For a discussion of this verse, see Chaitanya Charitamrita, Madhya-lila 17.133
 
Kali-santarana Upanisad from Krishna Yajur Veda
hare krishna hare krishna krishna krishna hare hare
hare rama hare rama rama rama hare hare
iti sodasakam namnam kali-kalmasa-nasanam
natah parataropayah sarva-vedesu drsyate
The sixteen names of the Hare Krishna maha-mantra: hare krishna hare krishna krishna krishna hare hare, hare rama hare rama rama rama hare hare destroy all the inauspiciousness of the age of Kali. This is the conclusion of all the Vedas. 
 
Agni Purana
hare krishna hare krishna krishna krishna hare hare
ratanti halaya vapi te krtartha na samsayah
Hare krishna hare krishna krishna krishna hare hare: Whoever chants this mantra, even neglectfully, will attain the supreme goal of life. Of this there is no doubt. 
 
Brahmanda Purana 6.59-60
nama sankirtana deva tarakam brahma drsyate
hare krishna hare krishna krishna krishna hare hare
hare rama hare rama rama rama hare hare
The nama sankirtana(public chanting) of Hare Krishna maha-mantradelivers a complete revelation of all of spiritual reality. 
 
Chaitanya-charitamrita, Antya-lila 3.257
mukti-hetuka tāraka haya 'rāma-nāma'
'kṛṣṇa-nāma' pāraka hañā kare prema-dāna
"The holy name of Lord Rāma certainly gives liberation, but the holy name of Kṛṣṇa transports one to the other side of the ocean of nescience and at last gives one ecstatic love of Kṛṣṇa." Chaitanya-charitamrita, Antya-lila 3.257
 
Padma Purana, Svarga Khanda 50.6
harir eva samaradhyah sarva deve suresvarah
hari nama maha mantrair nasyatpapa pisacakam
All the grievous sins of one who worships Lord Sri Hari, the Lord of all lords, and chants the holy name, the maha-mantra, are removed.
 
Ananta-samhita
hare krishna hare krishna krishna krishna hare hare
hare rama hare rama rama rama hare hare
sodasaitani namani dvatrimsad varnakani hi
kalau yuge maha-mantrah sammato jivatarane
varjayitva tu namaitad durjanaih parikalpitam
chandobaddham susiddhanta viruddham nabhyaset padam
tarakam brahma-namaitad brahmana gurunadina
kalisantaranadyasu sruti-svadhigatam hareh
praptam sri brahma-sisyena sri naradena dhimata
namaitad-uttamam srauta-paramparyena brahmanah
utsrjyaitan-maha-mantram ye tvanyat kalpitam padam
mahanameti gayanti te sastra-guru langhanah
tattva-virodha-sanprktam tadrsam daurjanam matam
sravatha pariharyam syadatma-hitarthina sada
hare krishna hare krishna krishna krishna hare hare
hare rama hare rama rama rama hare hare
 
“Hare krishna hare krishna krishna krishna hare hare, hare rama hare rama rama rama hare hare: This sixteen-name, thirty-two syllable mantra is the maha-mantra in the age of Kali by which all living beings can be delivered. One should never abandon chanting this maha-mantra and take to other so-called purificatory processes which are practiced by rascals, or engage in chanting other metrical compositions of the name of Krishna that are against the pure conclusions of the scriptures, or are filled with rasabhasa. About this divinely spiritual maha-mantra, which delivers one from material existence, the original guru, Lord Brahma, has said, kali-santararadi srutite, "The srutis have declared this mantra to be the best means of deliverance in the age of Kali". Having all heard this from Brahma, the sons and disciples of Brahma, beginning with Narada, all accepted the Hare Krishna maha-mantra and, having meditated on it, attained perfection.” 
Ananta-samhita is part of the Narada Pancaratra")
The maha-mantra is further mentioned in Chaitanya Charitamrita 1.7.83 (krishna-nama maha-mantrera), Chaitanya-charitamrita 3.9.56 ('hare krishna, hare krishna' kahe avisrama), Narada Pancaratra, etc.
 
Sri Vrindavana Mahimamrta by Srila Prabodhananda Sarasvati
hare krishna krsneti krsneti mukhyan
mahascarya-namavali-siddha-mantran
krpa-murti-caitanya-deva upagitan
kadabhyasya vrndavane syan krtarth
 
“When will my heart become satiated by perfecting the chanting of the Hare Krishna maha-mantra in Sri Vrndavana Dhama, which the most merciful Sri Caitanyadeva personally chanted and distributed to the fallen souls out of compassion? This wonderful maha-mantra is mixed with the mellows of love and is the chief and the perfection of all other mantras. They are full of spiritual energies and glories.” (Sri Vrindavana Mahimamrta by Srila Prabodhananda Sarasvati 17.89)
 
Srila Sarvabhauma Bhattacarya, Susloka-Satakam 23
hare krishna rama nama gana dana karinim
soka moha lobha tapa sarva vigna nasinim
pada padma lubdha bhakta vrnda bhakti dayinim
gaura murtim asu naumi nama sutra dharinim
 
"He makes the gift of the song of the names 'Hare, Krishna and Rama', and destroys all obstacles such as sorrow, delusion, greed and suffering. He gives the devotional service of Lord Krishna to the multitude of devotees who are eager for the shelter of His lotus feet. I fall down swiftly to offer my prostrated obeisances to the Lord in His golden form, who holds a string of meditation beads." 
 
Vasudev Ghosh's bhajan "Jaya Jagannatha Sacira-nandana", text 4
sri-radhar bhave ebe gora avatar
hare krishna nam gaura korila pracar
 
 
Chaitanya-bhagavata Madhya-khanda 23.75-80: (trans. Kusakratha Das)
75. The Lord personally taught them, "Please happily hear from Me themaha-mantra of Lord Krishna's names. It is:
76. Hare Krishna Hare Krishna Krishna Krishna Hare Hare Hare Rama Hare Rama Rama Rama Hare Hare
77. The Lord said, "Regularly chant japa of this maha-mantra.
78. In this way you will attain all perfections. Chant at any time and in any circumstance. There are no other rules for chanting.
79. Gather together, five or ten, in your own homes, clap hands and sing kirtana of these holy names.
80. You may also sing these words:
haraye namah krishna yadavaya namah gopala govinda rama sri-madhusudana
('I offer my respectful obeisances unto the Supreme Personality of Godhead, Krishna. He is the descendant of the Yadu family. Let me offer my respectful obeisances unto Gopala, Govinda, Rama and Sri Madhusudana.' Also see Chaitanya-charitamrita 2.26.64)
(Naradiya Purana, Prahlada-vakya)
81. Gathering at home with parents, wife, and children, please sing kirtana in this way."
 
japato hari namani sthane sata-gunadhikah
atmanam ca punaty-uccair-japan srotrn-punati ca
 
"Compared to that person who is attached to chanting japa, the person who performs loud chanting of the holy name of Sri Hari is one hundred times better. This is because the person who chants japa purifies himself, whereas the person who chants the holy name loudly in kirtana purifies himself, all those who are with him, and everyone else who hear the holy vibration." 
 
Chaitanya-bhagavata 1.16, Haridasa Thakura speaking
pasu-paksi-krma-adi balite na pare
sunile se harinama ta'ra saba tare
japile se krishna-nama apani se tare
ucca-sankirtane para-upakare kare
ata eva ucca kari' kirtana karile
sata-guna phala haya sarva-sastre bole
 
"The animals, birds, and insects cannot chant the holy name, but by hearing the holy name chanted they can benefit. Chanting the japa of the holy name of Krishna purifies oneself, but the loud sankirtana of the holy name of Krishna benefits all living beings. Therefore, loudly chant the holy name of Krishna in kirtana, and you will get one hundred times the benefit of chanting japa. This is the verdict of all the sastras."
"Listen my dear Misra, in Kali-yuga there is no need for severe penances or performance of opulent sacrifices; whoever worships the Supreme Lord Krishna he be crowned with fortune and success. So go back to your home and worship Lord Krishna with undeviating faith and attention, giving up falsehood and pretensions. By chanting the holy name of Lord Hari, Krishna, you will simultaneously obtain both the proper spiritual practice and the ultimate goal. 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. I am repeating this great chant for deliverance to you. This consists of sixteen names of the Supreme Lord with thirty two syllables: Hare Krishna Hare Krishna Krishna Krishna Hare Hare Hare Rama Hare Rama Rama Rama Hare Hare. By constantly chanting and worshiping this Maha Mantra, your heart will feel the first blossoming of love and God; then gradually you will understand the truth about the proper spiritual path and the ultimate spiritual goal." (Chaitanya-bhagavata 1.14, Lord Caitanya Mahaprabhu speaking to Tapana Misra)

In his purport to Caitanya-bhagavata Bhaktisiddhanta Sarasvati says very clearly that Haridasa Thakura chanted either loudly or softly and that is why his cave became Vaikuntha.
 
Chaitanya-bhagavata 1.16.172:
tabe haridasa ganga-tire gopha kari'
thakena virale ahar-nisa krishna smari'
 
"Then Haridasa went and found a cave on the bank of the Ganges. He remembered Krishna day and night as he resided alone in the cave."
Purport: "While remaining in a solitary cave on the bank of the Ganges at Phuliya, Srila Thakura Mahasaya loudly chanted the names of Krishna and passed his days and night remembering the pastimes of the Lord. Sometimes he would chant the sixteen name, thirty-two syllable, maha-mantra loudly (uccaihsvare), and sometimes he would chant softly (mrdusvare). Every day he would complete the chanting of three hundred thousand holy names, or in a year he would chant one hundred million names of Hari. Some people consider that chanting the names of Krishna in a solitary place is in the category of "upamsu-japa," or "chanting very mildly." They say that this maha-mantra, or chanting the holy names of the Lord, should not be heard by others; only the person who is chanting should hear. If the lips move, or if the holy names are recited, then they will automatically be heard by others. But if such persons lack faith in the Vaisnavas who chant the holy names of the Lord, then by the influence of Kali they dare to quarrel with those Vaisnava chanters."

Bhaktivinoda Thakura says in his song Sri Nama from Gitavali:
gay gora madhur sware
hare krishna hare krishna krishna krishna hare hare
hare rama hare rama rama rama hare hare
 
Lord Gaurasundara sings in a very sweet voice, Hare Krishna, Hare Krishna, Krishna Krishna, Hare Hare/ Hare Rama, Hare Rama, Rama Rama, Hare Hare.