Sunan an-Nasa'i, Book 46, Hadith 85 (In-Book) ⓘ
It was narrated that Ka'b said: "Whoever performs Wudu and performs Wudu well, then attends Isha prayer in congregation, then prays four similar Rakahs after that, reciting therein and bowing and prostrating perfectly, that will bring him a reward like that of (praying) Lailat Al-Qadar." (Hasan Maqtu)
أَخْبَرَنَا عَبْدُ الْحَمِيدِ بْنُ مُحَمَّدٍ، قَالَ حَدَّثَنَا مَخْلَدٌ، قَالَ حَدَّثَنَا ابْنُ جُرَيْجٍ، عَنْ عَطَاءٍ، عَنْ أَيْمَنَ، مَوْلَى ابْنِ عُمَرَ عَنْ تُبَيْعٍ، عَنْ كَعْبٍ، قَالَ مَنْ تَوَضَّأَ فَأَحْسَنَ وُضُوءَهُ ثُمَّ شَهِدَ صَلاَةَ الْعَتَمَةِ فِي جَمَاعَةٍ ثُمَّ صَلَّى إِلَيْهَا أَرْبَعًا مِثْلَهَا يَقْرَأُ فِيهَا وَيُتِمُّ رُكُوعَهَا وَسُجُودَهَا كَانَ لَهُ مِنَ الأَجْرِ مِثْلُ لَيْلَةِ الْقَدْرِ .
also referenced under: Hadith 4955 (Reference) & Volume 5, Book 46, Hadith 4958 (DarusSalam)