Narrated Abdullah bin Abbas: That Abu Sufyan told him that Heraclius said to him, "I asked you about the outcome of your battles with him (i.e. the Prophet ) and you told me that you fought each other with alternate success. So the Apostles are tested in this way but the ultimate victory is always theirs.
— Sahih Bukhari, Volume 4, Book 52: Fighting for the Cause of Allah (Jihaad), Hadith #60
Narrated Abdullah bin Abbas: That Abu Sufyan told him that Heraclius said to him, "I asked you about the outcome of your battles with him (i.e. the Prophet ) and you told me that you fought each other with alternate success. So the Apostles are tested in this way but the ultimate victory is always theirs.
This hadith is from the book of Fighting for the Cause of Allah (Jihaad) in Sahih Bukhari, compiled by Imam al-Bukhari. It is hadith number 60 in book 52 of volume 4.
