Verses from Vedic scriptures in glorification of the holy name
tunde tandavini ratim vitanute
karna-kroda-kadambini ghatayate
cetah-prangana-sangini vijayate
sarvendriyanam krtim
no jane janita kiyadbhir amrtaih
krsneti varna-dvayi
"I do not know how much nectar the two syllables 'Krs-na' have produced. When the holy name of Krsna is chanted, it appears to dance within the mouth. We then desire many, many mouths. When that name enters the holes of the ears, we desire many millions of ears. And when the holy name dances in the courtyard of the heart, it conquers the activities of the mind, and therefore all the senses become inert."
(Srila Rupa Goswami)
etavan eva loke 'smin
pumsam dharmah parah smrtah
bhakti-yogo bhagavati
Devotional service, beginning with the chanting of the holy name of the Lord, is the ultimate religious principle for the living entity in human society.
(Srimad Bhagvatam 6.3.22)
avasenapi yan-namni
kirtite sarva-patakaih
puman vimucyate sadyah
simha-trastair mrgair iva
"If one chants the holy name of the Lord, evenin a helpless condition or without desiring to do so, all the reactions of his sinful life depart, just as when a lion roars, all the small animals flee in fear."
(Garuda Purana)
apannah samsrtim ghoram
yan-nama vivaso grnan
tatah sadyo vimucyeta
yad bibheti svayam 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 Krsna, which is feared by fear personified.
(Srimad Bhagvatam 1.1.14)
sanketyam parihasyam va
stobham helanam eva va
asesagha-haram viduh
One who chants the holy name of the Lord is immediately freed from the reactions of unlimited sins, even if he chants indirectly to indicate something else, jokingly, for musical entertainment, or even neglectfully. This is accepted by all the learned scholars of the scriptures.
(Srimad Bhagvatam 6.2.14)
Om anavrttih sabdat By sound vibration, one becomes liberated. (Vedanta-sutra 4.4.22) It is stated also in the Vedanta-sutra that sound is the origin of all objects of material possession and that by sound one can also dissolve this material existence. Anavrttihsabdat means "liberation by sound." The entire material manifestation began from sound, and sound can also end material entanglement, if it has a particular potency. The  particular sound capable of doing this is the transcendental vibration Hare Krsna.
(Srila Prabhupada (SB purport 3.26.32))
jayati jayati namananda-rupam murarer
katham api sakrd attam mukti-dam praninam yat
pammam amrtam ekam jivanam bhusanam me
"All glories, all glories to the all blissful holy name of Sri Krsna, which causes the devotee to give up all conventional religious duties, meditation and worship. When somehow or other uttered even once by a living entity, the holy name awards him liberation. The holy name of Krsna is the highest nectar. It is my very life and my only treasure."  
(Brhad-bhagavatamrta 1.1.9) 
mantratas tantratas chidram
sarvam karoti nischidram
anusankirtanam tatva
There may be discrepancies in pronouncing the mantras and observing the regulative principles, and, moreover, there may be discrepancies in regard to time, place, person and paraphernalia. But when Your Lordship's holy name is chanted, everything becomes faultless.
(Srimad Bhagvatam 8.23.16)
krsna-varnam tvisakrsnam
yajnaih sanklrtana-prayair
yajanti hi su-medhasah
"In this Age of Kali, people who are endowed with sufficient intelligence will worship the Lord, who is accompanied by His associates, by performance of sainkirtana yajna."
(Srimad Bhagvatam 1l.5.32)
harer nama harer nama
harer namaiva kevalam
kalau nasty eva nasty eva
nasty eva gatir anyatha
"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. "
(Brhan-Naradiya Purana)
aho bata sva-paco to gariyan yaj-jihvagre nama tubhyam tepus tapas te "O my Lord, a person who is chanting Your holy name,although born of a low family like that of a candala [dog-eater], is situated on the hightest platform of self-realization. Such a person must have performed all kinds of  penances and sacrifices according to vedic rituals and studied the Vedic literatures many, many times after taking his bath in all the holy places of pilgrimage. Such a person is considered to be the best of the Aryan family.
(Srimad Bhagvatam 3.33.7)
na nama-sadrsam jnanam
na nama-sadrsam vratam
na nama sadrsam dhyanam
na nama sadrsam phalam
na nama sadrsas tyago
na nama sadrsah samah
na nama sadrsam punyam
na nama sadrsi gatih
namaiva parama muktir
namaiva parama gatih
niimaiva parama santir
namaiva parama sthitih
namaiva parama bhaktir
namaiva parama matih
niimaiva parama pritir
namaiva parama smrtih
ndmaiva karanam jantor
namaiva prabhur eva ca
namaiva paramaradhyam
namaiva paramo guruh
There is no vow like chanting the holy name, no knowledge superior to it, no meditation which comes anywhere near it, and it gives the highest result. No penance is equal to it, and nothing is as potent or powerful as the holy name.
Chanting is the greatest act of piety and the supreme refuge. Even the words of the Vedas do not possess sufficient power to describe its magnitude, chanting is the highest path to liberation, peace, and eternal life. It is the pinnacle  of devotion, the heart's joyous proclivity and attraction the best form of remembrance of the Supreme Lords. The holy name has appeared solely for the benefit of the living entities as th eir Lord and  master, their supreme worshipable object and their spiritual guide and mentor.
(Adi Purana)
om a'sya jananto nama
mahaste visnoh sumatim
bhajamahe am tat sat
"One who philosophically understands that the Lord's holy name and His potencies are the same can  properly approach and worship the Supreme Lord with transcendental knowledge and choice prayers."
(Rg Veda 1.56.3)
rg-vedo hi yajur-vedah
samavedapy' tharvanah
adhitastena yenoktam harir
ity aksara-dvayam
"The holy name is the essence of the Vedas, and far superior to it, anyone who doubts this faces constant misery. Pranava (the sound  om) is one of Krsna's names; the Vedas have emanated from this seed sound om, spoken first by Lord Brahma. One who continuously chants Lord Hari, Krsna's name, is considered to have mastered the four Vedas.
marco ma yajus ma sama
patha kincana
govindeti harermama geyam
gayasva nityasah
"What prompts you to undertake the tedious study of the four Vedas, namely, Rg, Sama, Yajur and Atharva? Simply go oon chanting ,"Govinda, Govinda!" That is all that is required to achieve perfection.
(Skanda Purana)