One verse

Srimad Bhagavatam 12.3.47

12.3.47

यथा हेम्नि स्थितो वह्निर्दुर्वर्णं हन्ति धातुजम् । एवमात्मगतो विष्णुर्योगिनामशुभाशयम् ॥ ४७ ॥

yathā hemni sthito vahnir durvarṇaṁ hanti dhātu-jam evam ātma-gato viṣṇur yoginām aśubhāśayam

yathā
just as
hemni
in gold
sthitaḥ
situated
vahniḥ
fire
durvarṇam
the discoloration
hanti
destroys
dhātu-jam
due to the taint of other metals
evam
in the same way
ātma-gataḥ
having entered the soul
viṣṇuḥ
Lord Viṣṇu
yoginām
of the yogīs
aśubha-āśayam
the dirty mind

Just as fire applied to gold removes any discoloration caused by traces of other metals, Lord Viṣṇu within the heart purifies the minds of the yogīs.