Sunan an-Nasa'i 4955
سنن النسائي#4955HasanIt 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)
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Abu GhuddahMaqtu
Al-AlbaniMaqtu
Zubair Ali ZaiHasan
In-book reference: 46:85