Sahih al-Bukhari 3880
صحيح البخاري#3880SahihNarrated Abu Huraira:that Allah's Messenger (ﷺ) informed them (i.e. his companions) of the death of Negus, the king of Ethiopia, on the very day on which the latter died, and said, "Ask Allah's Forgiveness for your brother
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Every narration in Sahih al-Bukhari is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 63:105