The Book of Prayer - Travellers
6/25. Chapter:
Encouragement to pray qiyam during Ramadan, which is Tarawih
Sahih Muslim
وَحَدَّثَنِي زُهَيْرُ بْنُ حَرْبٍ، حَدَّثَنَا مُعَاذُ بْنُ هِشَامٍ، حَدَّثَنِي أَبِي، عَنْ يَحْيَى بْنِ أَبِي كَثِيرٍ، قَالَ حَدَّثَنَا أَبُو سَلَمَةَ بْنُ عَبْدِ الرَّحْمَنِ، أَنَّ أَبَا هُرَيْرَةَ، حَدَّثَهُمْ أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ " مَنْ صَامَ رَمَضَانَ إِيمَانًا وَاحْتِسَابًا غُفِرَ لَهُ مَا تَقَدَّمَ مِنْ ذَنْبِهِ وَمَنْ قَامَ لَيْلَةَ الْقَدْرِ إِيمَانًا وَاحْتِسَابًا غُفِرَ لَهُ مَا تَقَدَّمَ مِنْ ذَنْبِهِ " .
Abu Huraira reported Allah's Messenger (ﷺ) as saying: He who observed the fasts of Ramadan with faith and seeking reward (from Allah), all his previous sins would be forgiven, and he who observed prayer on Lailat-ul- Qadr with faith and seeking reward (from Allah), all his previous sins would be forgiven.
Reference : Sahih Muslim 760aIn-book reference : Book 6, Hadith 209USC-MSA web (English) reference : Book 4, Hadith 1664