Sahih al-Bukhari 2804
صحيح البخاري#2804SahihNarrated `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 (ﷺ) ) 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
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Every narration in Sahih al-Bukhari is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 56:21