SB 7.10.19

yatra yatra ca mad-bhaktāḥ
 praśāntāḥ sama-darśinaḥ
sādhavaḥ samudācārās
 te pūyante ’pi kīkaṭāḥ
Word for word: 
yatra yatra — wherever and whenever; ca — also; mat-bhaktāḥ — My devotees; praśāntāḥ — extremely peaceful; sama-darśinaḥ — equipoised; sādhavaḥ — decorated with all good qualities; samudācārāḥ — equally magnanimous; te — all of them; pūyante — are purified; api — even; kīkaṭāḥ — a degraded country or the inhabitants of such a place.
Translation: 
Whenever and wherever there are peaceful, equipoised devotees who are well-behaved and decorated with all good qualities, that place and the dynasties there, even if condemned, are purified.
Purport: 

Wherever exalted devotees stay, not only they and their dynasties but the entire country is purified.