Sayyiduna Anas (may Allah be pleased with him) narrates: When the Prophet (peace and blessings be upon him) received news of the death of the Negus (al-Najashi), he offered the funeral prayer for him. It was said: "O Messenger of Allah! Are you offering the funeral prayer for an Abyssinian man?" So Allah Almighty revealed this verse: "Among the People of the Book are some who believe in Allah."
Imam Bazzar and Imam Tabarani in al-Mu'jam al-Awsat recorded it. Tabarani's narrators are thiqat (trustworthy).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الجنائز / 4201