One verse

Srimad Bhagavatam 6.1.16

6.1.16

न तथा ह्यघवान् राजन्पूयेत तपआदिभि: । यथा कृष्णार्पितप्राणस्तत्पुरुषनिषेवया ॥ १६ ॥

na tatha hy aghavan rajan puyeta tapa-adibhih yatha krsnarpita-pranas tat-purusa-nisevaya

na
not
tatha
so much
hi
certainly
agha-van
a man full of sinful activities
rajan
O King
puyeta
can become purified
tapah-adibhih
by executing the principles of austerity, penance, brahmacarya and other purifying processes
yatha
as much as
krsna-arpita-pranah
the devotee whose life is fully Krsna conscious
tat-purusa-nisevaya
by engaging his life in the service of Krsna’s representative.

My dear King, if a sinful person engages in the service of a bona fide devotee of the Lord and thus learns how to dedicate his life unto the lotus feet of Krsna, he can be completely purified. One cannot be purified merely by undergoing austerity, penance, brahmacarya and the other methods of atonement I have previously described.