CC Madhya 8.251
‘kṛṣṇa-bhakta-saṅga vinā śreyaḥ nāhi āra’
śreyaḥ-madhye — among beneficial activities; kona — which; śreyaḥ — beneficial function; jīvera — of the living entity; haya — is; sāra — the essence; kṛṣṇa-bhakta-saṅga — for associating with the devotees of Lord Kṛṣṇa; vinā — except; śreyaḥ — beneficial activity; nāhi — there is not; āra — another.
Then Śrī Caitanya Mahāprabhu asked, “Out of all auspicious and beneficial activities, which is best for the living entity?”
Rāmānanda Rāya replied, “The only auspicious activity is association with the devotees of Kṛṣṇa.”
According to Śrīmad-Bhāgavatam (11.2.30):
saṁsāre ’smin kṣaṇārdho ’pi sat-saṅgaḥ śevadhir nṛṇām
“We are asking you to tell us what is the most perfect welfare activity. I think that in this material world, association with devotees — even if it be for a moment — is the greatest treasure house for mankind.”