From Sahih Muslim (Hadith 2205):
Abu Huraira reported:The Messenger of Allah (ﷺ) gave us the news of the death of Negus, the ruler of Abyssinia, on the day when he died, and he said (to us): Beg pardon for your brother. Ibn Shihab said that Sa'id b. Musayyib had told that Abu Huraira had narrated to him that the Messenger of Allah (ﷺ) drew them up in a row in a place of prayer, and offered prayer and recited four takbirs for him
Reference: Muslim 2205