The Book of Jihad and Expedition (Kitab Al-Jihad wa'l-Siyar)
Muslim :: Book 19 : Hadith 4383
The tradition has been narrated on the authority of Anas b. Malik (the same narrator) through a different chain of transmitters, but this version does not mention:" And he was not the Negus for whom the Prophet (may peace be upon him) had said the funeral prayers."