Sunan an-Nasa'i 2197
سنن النسائي#2197Sahihأَخْبَرَنَا أَبُو دَاوُدَ، قَالَ حَدَّثَنَا يَعْقُوبُ بْنُ إِبْرَاهِيمَ، قَالَ حَدَّثَنَا أَبِي، عَنْ صَالِحٍ، عَنِ ابْنِ شِهَابٍ، أَنَّ أَبَا سَلَمَةَ، أَخْبَرَهُ أَنَّ أَبَا هُرَيْرَةَ قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " مَنْ قَامَ رَمَضَانَ إِيمَانًا وَاحْتِسَابًا غُفِرَ لَهُ مَا تَقَدَّمَ مِنْ ذَنْبِهِ " .
It was narrated from Ibn Shahab that Abu Salamah told him 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
Scholarly Authentication
The label above is the grade most of these scholars gave — one dissenting opinion no longer speaks for all of them. If any scholar calls a narration fabricated, that verdict is shown instead, whatever the others say. Each scholar's own wording:
In-book reference: 22:108