Bulugh al-Maram, Book 5, Hadith 717 (English) ⓘ
Abu Hurairah narrated that The Messenger of Allah said: “Whoever prays during the night in Ramadan out of sincere faith and seeking its reward from Allah, will have all of his previous sins forgiven." Agreed upon.
عَنْ أَبِي هُرَيْرَةَ - رضى الله عنه - أَنَّ رَسُولَ اَللَّهِ - صلى الله عليه وسلم -قَالَ: { مَنْ قَامَ رَمَضَانَ إِيمَانًا وَاحْتِسَابًا, غُفِرَ لَهُ مَا تَقَدَّمَ مِنْ ذَنْبِهِ } مُتَّفَقٌ عَلَيْهِ 1. 1 - صحيح. رواه البخاري ( 2009 )، ومسلم ( 759 ).
also referenced under: Book 5, Hadith 697 (In-Book)