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 Kṛṣṇa, 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.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
न तथा ह्यघवान् राजन् पूयेत तप आदिभिः । यथा कृष्णार्पितप्राणस्तत्पूरुषनिषेवया
na tathā hyaghavān rājan pūyeta tapa ādibhiḥ | yathā kṛṣṇārpitaprāṇastatpūruṣaniṣevayā
SB 6.1.16