(Imam Bukhari narrates that) Abu Al-Yaman narrated to us, he said: Shu'aib informed us, he said: Abu Az-Zinad narrated to us, from Al-A'raj, from Hazrat Abu Hurairah (may Allāh be pleased with him), that the Messenger of Allāh ﷺ said:
Whoever stood (in prayer) on Lailat-ul-Qadr with faith and seeking reward, his previous sins are forgiven.
حَدَّثَنَا أَبُو الْيَمَانِ قَالَ: أَخْبَرَنَا شُعَيْبٌ قَالَ: حَدَّثَنَا أَبُو الزِّنَادِ، عَنِ الْأَعْرَجِ، عَنْ أَبِي هُرَيْرَةَ قَالَ: قَالَ رَسُولُ اللهِ ﷺ
مَنْ يَقُمْ لَيْلَةَ الْقَدْرِ إِيمَانًا وَاحْتِسَابًا غُفِرَ لَهُ مَا تَقَدَّمَ مِنْ ذَنْبِهِ.
Reference: Sahih Al Bukhari 35