One verse

Srimad Bhagavatam 6.5.26

6.5.26

तदुपस्पर्शनादेव विनिर्धूतमलाशया: । जपन्तो ब्रह्म परमं तेपुस्तत्र महत्तप: ॥ २६ ॥

tad-upasparsanad eva vinirdhuta-malasayah japanto brahma paramam tepus tatra mahat tapah

tat
of that holy place
upasparsanat
by bathing regularly in the water
eva
indeed
vinirdhuta
completely purified
mala-asayah
of all the dirt within the heart
japantah
chanting or murmuring
brahma
mantras beginning with om (such as om tad visnoh paramam padam sada pasyanti surayah)
paramam
the ultimate goal
tepuh
performed
tatra
there
mahat
great
tapah
penances.

At Narayana-saras, the second group of sons performed penances in the same way as the first. They bathed in the holy water, and by its touch all the dirty material desires in their hearts were cleansed away. They murmured mantras beginning with omkara and underwent a severe course of austerities.