Reward for Reciting Ayatul-Kursi after every obligatory Prayers

Abu Umaamah (RA) narrated that:
The Prophet (صلى الله عليه وسلم) said:
“Whoever reads “Ayatul-Kursi” [Qur’an 2:255], after every obligatory prayer, nothing prevents him from entering Paradise except death (i.e. that he is still alive).”
(An-Nasaa’ee, Ibn Hibbaan – Sahih)

We have not come across what you mentioned except what is reported regarding Aayatul-Kursi [Quran 2:255]. Ibn Hibbaan reported that the Prophet said: “Whoever recites Ayatul-Kursi after each obligatory prayer, then nothing can prevent him from entering Paradise except death.”