Sayyiduna Abu Sa'id al-Khudri (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 said: "Go out and offer the funeral prayer for your brother whom you have never seen." So we went out. The Prophet (peace and blessings be upon him) stepped forward and we formed rows behind him. He prayed and we prayed too. When we had finished the prayer, the hypocrites said: "Look at him! He went out and offered the funeral prayer for a powerful Christian man (that is, a ruler) whom he has never even seen." So Allah Almighty revealed this verse: "Indeed, among the People of the Book are some who believe in Allah" (to the end of the verse).
Imam Tabarani recorded it in al-Mu'jam al-Awsat. Its chain contains a narrator, Abd al-Rahman bin Abi al-Zinad, and he is da'if (weak).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الجنائز / 4203