Prithu Maharaja is very emphatic in this connection — only an animal can give up the practice of chanting Hare Krishna. Those who are not animals but actually intelligent, advanced, human, civilized men cannot give up this practice of continually chanting Hare Krishna, Hare Krishna, Krishna Krishna, Hare Hare/ Hare Rama, Hare Rama, Rama Rama, Hare Hare.
Purport on Srimad Bhagavatam 4.20.26
In this horrible condition of life there is only one way of liberation—to engage in the activities of transcendental chanting and hearing of the holy name of the Supreme Lord.
Purport on Srimad Bhagavatam 4.7.44
The main purpose of sannyasa life is to be in constant companionship with the Supreme Lord, either by thinking of Him within the heart or hearing of Him through aural reception.
Purport on SB 3.24.35
Srimad Bhagavatam it is repeatedly and clearly said that the essence of religion in the Age of Kali is the chanting of the holy name of Krishna.
Caitanya Caritamrta Adi lila 3.50
In its present condition, the world can only be saved by introducing this sankirtana, this Krishna consciousness movement.
Purport on Srimad Bhagavatam 4.18.8
When a Vedic mantra is chanted within the mouth so that only the chanter can hear, the chanting is called japa. But when such mantras are chanted loudly, it is called kirtana.
Purport on Srimad Bhagavatam 3.14.32