It was narrated from Abu Hurairah that the Messenger of Allah (ﷺ) said:‘Whoever fasts Ramadan out of faith and the hope of reward will be forgiven his previous sins.”
Hadith No. 1641
Sunan Ibn Majah
Gradings:
Al-Albani:
Sahih
Muhammad Fouad Abd al-Baqi:
Sahih
Shuaib Al Arnaut:
Sahih
Zubair Ali Zai:
Sahih - Bukhari And Muslim