Sunan an-Nasa'i 2205
سنن النسائي#2205SahihIt was narrated that Abu Hurairah said:"The Messenger of Allah said: 'Whoever fasts Ramadan out of faith and in the hope of reward, he will be forgiven his previous sins
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Abu GhuddahSahih
Al-AlbaniSahih
Zubair Ali ZaiSahih Bukhari
In-book reference: 22:116