(26) باب كِتَابِ النَّبِيِّ صلى الله عليه وسلم إِلَى هِرَقْلَ يَدْعُوهُ إِلَى الإِسْلاَمِ
This hadith has been narrated on the authority of Ibn Shihab with the same chain of transmitters but with the addition:
" When Allah inflicted defeat on the armies of Persia, Caesar moved from Hims to Aelia (Bait al-Maqdis) for thanking Allah as He granted him victory." In this hadith these words occur:" From Muhammad, servant of Allah and His Messenger," and said:" The sin of your followers," and also said the words:" to the call of Islam".
Reference: Sahih Muslim 1773 b
In-book reference: Book 32, Hadith 90
USC-MSA web (English) reference(deprecated numbering scheme): Book 19, Hadith 4381