Sunan an Nasai 2197
The Book of Fasting
أَخْبَرَنَا 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
Grading: Abu Ghuddah: Sahih · Al-Albani: Sahih · Zubair Ali Zai: Hasan
Text from the public-domain hadith-api dataset. Numbering follows that dataset and can differ by a few from some printed editions — check the wording, not only the number.