Sahih Muslim Book 19, Hadith Number 4383.

Chapter : Letters of the Holy Prophet (may peace be upon him) to the kings of disbelievers inviting them to Allah, the Exalted and Glorious.

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.”