CC Ādi 13.66
kṛṣṇa-kathā, kṛṣṇa-pūjā, nāma-saṅkīrtana
In the house of Advaita Ācārya, all the Vaiṣṇavas took pleasure in always talking of Kṛṣṇa, always worshiping Kṛṣṇa and always chanting the Hare Kṛṣṇa mahā-mantra.
On these principles only does the Kṛṣṇa consciousness movement go on. We have no business other than to talk of Kṛṣṇa, worship Kṛṣṇa and chant the Hare Kṛṣṇa mahā-mantra.