हरेर्नाम हरेर्नाम हरेर्नामैव केवलम् ।
कलौ नास्त्येव नास्त्येव नास्त्येव गतिरन्यथा ॥
harer nāma harer nāma harer nāmaiva kevalam |
kalau nāsty eva nāsty eva nāsty eva gatir anyathā ||
(Bṛhan-Nāradīya-purāṇa; cited in Bhakti Sandarbha: 273; Caitanya-caritāmṛta: 1.7.76, 1.17.21, 2.6.242)
“The name of Hari, the name of Hari—certainly the name of Hari alone—in the Age of Kali, there is certainly no, there is certainly no, there is certainly no way otherwise.”
Commentary
kali-kāle nāma-rūpe kṛṣṇa-avatāra |
nāma haite haya sarva-jagat-nistāra ||
dārḍhya lāgi harer nāma-ukti tina-vāra |
jaḍa-loka bujhāite punaḥ eva-kāra ||
kevala-śabde punar api niścaya-karaṇa |
jñāna-yoga-tapa-ādi karma nivāraṇa ||
anyathā ye māne, tāra nāhika nistāra |
nāhi nāhi nāhi e tina eva-kāra ||
(Caitanya-caritāmṛta: 1.17.22–25)
“In the Age of Kali, Kṛṣṇa’s avatāra is in the form of his name. Deliverance of the entire world occurs because of his name. Mention of ‘Hari’s name’ (Harer nāma) occurs three times [in the verse from Bṛhan Nāradīya Purāṇa] for the sake of firmness. To make dull people understand, the word eva [“certainly”] is also stated. The word kevala [“alone”] is also stated as well for the purpose of certainty, that is, for excluding karma, jñāna, yoga, austerity (tapa), and so forth [from being regarded as the sādhana to be followed in the Age of Kali]. There is no deliverance for one who thinks otherwise [i.e., for one does not take shelter in Hari’s name]. [Thus,] ‘There is no,’ ‘There is no,’ ‘There is no,’ [is stated] thrice with word eva [“certainly”].”
See also the following section in Śrī Caitnaya-caritāmṛta where the manner in which one should take shelter in Hari’s name is taught.