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
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
Lord Chaitanya, however, has recommended only one yajna, or sacrifice, called the sankirtana-yajna, the chanting of Hare Krishna, in which everyone can take part. Thus both devotees and fruitive workers can derive equal benefit from the performances of sankirtana-yajna.
Purport on Srimad bhagavatam 1.16.20
In this age of Kali there is no other religion but the glorification of the Lord by utterance of His holy name, and that is the injunction of all the revealed scriptures.
Of the nine processes of devotional service, the most important is to always chant the holy name of the Lord. If one does so, avoiding the ten kinds of offenses, one very easily obtained the most valuable love of Godhead.
Chaitanya Caritamrta Antya Lila 4.71