Sunan an-Nasa'i 1602
سنن النسائي#1602SahihIt was narrated from Abu Hurairah that:The Messenger of Allah (ﷺ) said: "Whoever prays Qiyam during 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 ZaiHasan
In-book reference: 20:5