Best Purifier of all Sins

Devotion to God is the supreme purifier of all the sins that a person commits in his life time. 

In Bhagavad Gita God himself is giving that assurance

Bhagavad Gita Chapter 9


TEXT 30

api cet su-duracaro 
bhajate mam ananya-bhak 
sadhur eva sa mantavyah 
samyag vyavasito hi sah


SYNONYMS
 
api--in spite of; cet--although; su-duracarah--one committing the most abominable actions; bhajate--engaged in devotional service; mam--unto Me; ananya-bhak--without deviation; sadhuh--saint; eva--certainly;sah--he; mantavyah--to be considered; samyak--completely;vyavasitah--situated; hi--certainly; sah--he.

TRANSLATION
 
Even if one commits the most abominable actions, if he is engaged in devotional service, he is to be considered saintly because he is properly situated.


Through the above verse, Krishna is telling Arjuna that even if the most sinful of person worships Him with full devotion, then He considers him to be a saint as he has rightly resolved in his life.
Let's all be devotees of the supreme personality of godhead, Lord Krishna.