´Abu Salamah bin 'Abdur-Rahman narrated that Abu Hurairah said:` "I heard the Messenger of Allah say concerning Ramadan: 'Whoeve spends its nights in prayer (Qiyam) out of faith and in the hope of reward, he will be forgiven his previous sins." '
Hadith ReferenceSunan an-Nasa'i / The Book of Fasting / Hadith: 2198
Hadith Gradingالألبانی:صحيح | زبیر علی زئی:إسناده صحيح