A.C. Bhaktivedanta Swami Prabhupada
In this age, chanting of Hare Krishna Mantra is the prime business of the devotee, and preaching of this Hare Krishna Mantra by outdoor Sankirtana and propagation of literature is our more important business. Side by side, Deity worship is recommended, but when there is a question of accepting one of them, we shall prefer to accept chanting of Hare Krishna Mantra first.
Letter to Hamsaduta – Hamburg 5 September, 1969.
Radhanath Swami
The holy name does not kill the demon. It kills the demonic tendency in the heart of the demon that awakens pure love with pure compassion of the soul.
A.C. Bhaktivedanta Swami Prabhupada, Picture Quotes

Cut the Anarthas with Scissor of Holy names of the Lord.
Lord Krishna, Picture Quotes

Of sacrifices I am the chanting of the holy names [japa].
Bhagavat Gita 10.25
A.C. Bhaktivedanta Swami Prabhupada, Nectar of Devotion, Picture Quotes

Caitanya Mahaprabhu has recommended that everyone chant the Hare Krishna mantra just to cleanse the dust from the heart. If the dust of the heart is cleansed away, then one can actually understand the importance of the holy name.
Nectar of Devotion, Chapter 12,
Srila Prabhupada
Picture Quotes, Srimad Bhagavatam

What is the power of Lord’s name ? The process of chanting the holy name of the Lord is so powerful that by this chanting even householders can very easily gain the ultimate result achieved by persons in the renounced order.