Sahih al-Bukhari
Volume # 1
Hadith # 37
Narrated by: Abu Huraira (RA)

Allah's Apostle (SAW) said, "Whoever observes fasts during the month of Ramadan out of sincere faith, and hoping to attain Allah's rewards, then all his past sins will be forgiven."

Sahih al Bukhari Hadith
Volume # 9
Hadith # 21
Narrated by: Ibn Abbas (RA)

The Prophet (SAW) said, "The most hated persons to Allah are three:

(1) A person who deviates from the right conduct, i.e., an evil doer, in the Haram (sanctuaries of Mecca and Medina);
(2) a person who seeks that the traditions of the Pre-Islamic Period of Ignorance, should remain in Islam
(3) and a person who seeks to shed somebody's blood without any right."