Bhagavat Purana – 11.5.32
kṛṣṇa-varṇaḿ tviṣākṛṣṇaḿ sāńgopāńgāstra-pārṣadam
yajñaiḥ sańkīrtana-prāyair yajanti hi su-medhasaḥ
Always vibrating the sound “Krsna” – but with a golden color that is just the opposite of Krnsa – along with his associates, servants, weapons, and confidants… those who worship this sacrifice of chanting “Krsna” called SANKIRTAN are certainly the most intelligent people.
Bhagavat Purana 12.3.51
kaler doṣa-nidhe rājann asti hy eko mahān guṇaḥ
kīrtanād eva kṛṣṇasya mukta-bandhaḥ paraḿ vrajet
Kali-yuga [Our current historical epoch] is an ocean of problems, but there is certainly one very great thing about it: simply by doing KIRTAN one can get liberated and attain the supreme goal.
Bhagavat Purana 12.3.52
kṛte yad dhyāyato viṣṇuḿ tretāyāḿ yajato makhaiḥ
dvāpare paricaryāyāḿ kalau tad dhari-kīrtanāt
In Krita Yuga, by meditating on Vishnu. In Treta Yuga by worshipful sacrifices. In Dvapara Yuga by worship of the Deity. In Kali, all that, by HARI-KIRTAN.
Vishnu Purana 6.2.17 / Padma Purana Uttara:72.25 / Brihan Naradiya Purana 38.97
dhyāyan kṛte yajan yajñais tretāyāḿ dvāpare ‘rcayan
yad āpnoti tad āpnoti kalau sańkīrtya keśavam
By meditation in Krita Yuga. By sacrifice in Treta Yuga. By worship in Dvapara Yuga… whatever those can achieve is gotten in Kali Yuga by KESHAVA SANKIRTANA.
Bhagavat Purana 11.5.36
kaliḿ sabhājayanty āryā guṇa-jñāḥ sāra-bhāginaḥ
yatra sańkīrtanenaiva sarva-svārtho ‘bhilabhyate
Kali Yuga… very refined and advanced people who know the essence of good fortune worship this age of history, knowing well its great quality. In this age, SANKIRTANA certainly grants all goals of life.