(122) بَابُ قَوْلِ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «نُصِرْتُ بِالرُّعْبِ مَسِيرَةَ شَهْرٍ»
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.' "
Reference: Sahih al-Bukhari 2978
In-book reference: Book 56, Hadith 187
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 4, Book 52, Hadith 221