Sahih al-Bukhari 35
Sahih al-Bukhari · Book 2: Belief · To establish the (Nawafil - voluntary) prayers on the night of Qadr is a part of faith
Narrated Abu Huraira:
حَدَّثَنَا أَبُو الْيَمَانِ ، قَالَ أَخْبَرَنَا شُعَيْبٌ ، قَالَ حَدَّثَنَا أَبُو الزِّنَادِ ، عَنِ الأَعْرَجِ ، عَنْ أَبِي هُرَيْرَةَ ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " مَنْ يَقُمْ لَيْلَةَ الْقَدْرِ إِيمَانًا وَاحْتِسَابًا غُفِرَ لَهُ مَا تَقَدَّمَ مِنْ ذَنْبِهِ " .
Allah's Messenger (ﷺ) said, "Whoever establishes the prayers on the night of Qadr out of sincere faith and hoping to attain Allah's rewards (not to show off) then all his past sins will be forgiven."