Jami` at-Tirmidhi 2716
جامع الترمذي#2716SahihNarrated Anas bin Malik:"Before he died, the Messenger of Allah (ﷺ) had written to Kisra, Ceasar, An-Najashi, and to every tyrant calling them to Allah. This An-Najashi is not the one that the Prophet (ﷺ) performed to the funeral Salat for
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Ahmad Muhammad ShakirSahih
Al-AlbaniSahih
Bashar Awad MaaroufHasan Sahih
Zubair Ali ZaiSahih Muslim
In-book reference: 42:29