The Book of Qiyam Al-Lail (The Night Prayer) and Voluntary Prayers During the Day
20/3. Chapter:
The reward of one who prays Qiyam during Ramadan out of faith and in the hope of reward
Sunan an-Nasai
أَخْبَرَنَا قُتَيْبَةُ، عَنْ مَالِكٍ، عَنِ ابْنِ شِهَابٍ، عَنْ حُمَيْدِ بْنِ عَبْدِ الرَّحْمَنِ، عَنْ أَبِي هُرَيْرَةَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ " مَنْ قَامَ رَمَضَانَ إِيمَانًا وَاحْتِسَابًا غُفِرَ لَهُ مَا تَقَدَّمَ مِنْ ذَنْبِهِ " .
It was narrated from Abu Hurairah that: The Messenger of Allah (ﷺ) said: "Whoever prays Qiyam during Ramadan out of faith and in the hope of reward, he will be forgiven his previous sins."
Reference : Sunan an-Nasa'i 1602In-book reference : Book 20, Hadith 5English translation : Vol. 2, Book 20, Hadith 1603