The Book of Prayers (Kitab Al-Salat)
Muslim :: Book 4 : Hadith 2078
Abu Huraira reported: The Messenger of Allah (may peace be upon him) 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 (may peace be upon him) drew them up in a row in a place of prayer, and offered prayer and recited four takbirs for him.