Sunan an-Nasa'i 2201
سنن النسائي#2201SahihIt was narrated from Abu Hurairah that the Messenger of Allah said:"Whoever spends the night of Ramadan in prayer (Qiyam) 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
In-book reference: 22:112