It wasnarrated from Abu Hurairah that the Messenger of Allah (ﷺ)said:
'Whoever fasts Ramadan out of faith and the hope of reward willbeforgiven his previous sins." (ID)
English reference (ID): Vol. 1, Book 7, Hadith 1641 (ID)
Arabic reference (ID): Book 7, Hadith 1710 (ID)