Sunan an-Nasa'i 2207
سنن النسائي#2207SahihIt was narrated that Abu Hurairah said:"The Messenger of Allah said: 'Whoever spends the nights of Ramadan in prayer (Qiyam) out of faith and in the hope of reward, he will be forgiven his previous sins, and whoever spends the night of Lailat Al-Qadr in prayer 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 ZaiHasan
In-book reference: 22:118