Sahih Bukhari Volume 004, Book 052, Hadith Number 221.
Hadith Section/Book: Sahih Bukhari Sahih Bukhari Book 52. Fighting for the Cause of Allah (Jihaad)
Narated By 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 Apostle 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.'"