Story of Rishi Balmiki :
In ancient times in India, there was a robber named Ratnakar who lived in the forests. He was a cruel hunter and a robber who did all the heinous Karmas in life. Everyone in the forest, from birds to animals to humans was afraid of him. One day, he was looking for a victim in the forest, when he came into contact with great sage Narada, who was chanting the names of God. Ratnakar wanted to rob him but sage Narada advised him to stop stealing and killing the creatures as it was a very sinful act. He advised Ratnakar to start meditating & chanting the names of Lord Rama. Somehow he could not chant the name of Rama so he advised him to chant “Mara, Mara”, which he chanted but it responded in a reverse sequence like Rama, Rama only. Through reciting the names of Lord Rama he became a great saint who wrote the great epic ‘Ramayana’.
Story of Angulimala :
Similarly in the times of Lord Buddha, there was a deadly robber named Angulimala. He was so cruel that after looting people, he used to cut the fingers of people & take it with him. Once that robber and murderer came into contact with Lord Buddha & got converted to monkhood and later to sainthood. Lord Buddha did not judge Angulimala from his appearances and his external behavior. but saw the potential to reform him & make him a saint & did so by his divine capacity.
In Bhagwat Gita also, God assures his disciple Arjuna in many ways & asks him to take refuge in Him & says that He shall emancipate him of sin in all the ways, shall rescue him in his life always. Many times we think that we have done many sins in life & how God shall accept us, but God makes it very clear in Bhagwat Gita that once a person becomes devoted to Him, He does not consider that person a sinner, rather God considers that person to be a Saint as he has taken the right decision in his life to become devoted to God.
Api chet su-duracharo
bhajate maam ananya-bhak
sadhurev sa mantavya
samyag vyvasito hi sah' (Gita: Chapter IX verse 30)
'Even if the vilest sinner worships Me with full devotion, he should be considered a noble soul or saint; as he has taken the right step by worshipping me.'
'kshipram bhavti dharmatma
na me bhaktah pranashyati' (Gita: Chapter IX verse 31)
'He speedily becomes virtuous and secures lasting peace. O son of Kunti, know it for certain that My devotee never falls.'
Through above verse 31, God is telling Arjuna that such a sinful person after becoming His devotee becomes a person of good virtues and always remains in peace & such a peace is not temporary but is ever lasting. God is assuring the son of Kunti (another name of Arjuna, his disciple) that his devotee never falls again in life as He always protects him. So let's all worship the God always so that He can protect us always.
Jai Sri Krishna