Narrated Ibn `Abbas:Abu Sufyan said, "Heraclius sent for me when I was in 'llya' (i.e. Jerusalem). Then he asked for the letter of Allah's Messenger (ﷺ) and when he had finished its reading there was a great hue and cry around him and the voices grew louder and we were asked to quit the place. When we were turned out, I said to my companions, 'The cause of Ibn Abi Kabsha has become conspicuous as the King of Bani Al- Asfar is afraid of him.' "
حَدَّثَنَا أَبُو الْيَمَانِ، أَخْبَرَنَا شُعَيْبٌ، عَنِ الزُّهْرِيِّ، قَالَ أَخْبَرَنِي عُبَيْدُ اللَّهِ بْنُ عَبْدِ اللَّهِ، أَنَّ ابْنَ عَبَّاسٍ ـ رضى الله عنهما ـ أَخْبَرَهُ أَنَّ أَبَا سُفْيَانَ أَخْبَرَهُ أَنَّ هِرَقْلَ أَرْسَلَ إِلَيْهِ وَهُمْ بِإِيلِيَاءَ، ثُمَّ دَعَا بِكِتَابِ رَسُولِ اللَّهِ صلى الله عليه وسلم، فَلَمَّا فَرَغَ مِنْ قِرَاءَةِ الْكِتَابِ كَثُرَ عِنْدَهُ الصَّخَبُ، فَارْتَفَعَتِ الأَصْوَاتُ، وَأُخْرِجْنَا، فَقُلْتُ لأَصْحَابِي حِينَ أُخْرِجْنَا لَقَدْ أَمِرَ أَمْرُ ابْنِ أَبِي كَبْشَةَ، إِنَّهُ يَخَافُهُ مَلِكُ بَنِي الأَصْفَرِ.
Bukhari
Fighting for the Cause of Allah (Jihaad) • Hadith 187