كتاب الجهاد والسير
32
The Book of Jihad and Expeditions
(27)
Chapter: The Prophet (saws) wrote to the Kings of the Kuffar, inviting them to Islam
(27)
باب كُتُبِ النَّبِيِّ صلى الله عليه وسلم إِلَى مُلُوكِ الْكُفَّارِ يَدْعُوهُمْ إِلَى اللَّهِ عَزَّ وَجَلَّ

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 (ﷺ) had said the funeral prayers."
وَحَدَّثَنَاهُ مُحَمَّدُ بْنُ عَبْدِ اللَّهِ الرُّزِّيُّ، حَدَّثَنَا عَبْدُ الْوَهَّابِ بْنُ عَطَاءٍ، عَنْ سَعِيدٍ، عَنْ قَتَادَةَ، حَدَّثَنَا أَنَسُ بْنُ مَالِكٍ، عَنِ النَّبِيِّ صلى الله عليه وسلم ‏.‏ بِمِثْلِهِ وَلَمْ يَقُلْ وَلَيْسَ بِالنَّجَاشِي الَّذِي صَلَّى عَلَيْهِ النَّبِيُّ صلى الله عليه وسلم ‏.‏
Reference : Sahih Muslim 1774 b
In-book reference : Book 32, Hadith 92
USC-MSA web (English) reference : Book 19, Hadith 4383
  (deprecated numbering scheme)