Sahih al-Bukhari 2804
Sahih al-Bukhari · Book 56: Fighting for the Cause of Allah (Jihaad) · The Statement of Allah Aza wa'jal: "Say: Do you wait for us except one of the two best things (martyrdom or victory)?..."
Narrated `Abdullah bin `Abbas:
حَدَّثَنَا يَحْيَى بْنُ بُكَيْرٍ ، حَدَّثَنَا اللَّيْثُ ، قَالَ حَدَّثَنِي يُونُسُ ، عَنِ ابْنِ شِهَابٍ ، عَنْ عُبَيْدِ اللَّهِ بْنِ عَبْدِ اللَّهِ ، أَنَّ عَبْدَ اللَّهِ بْنَ عَبَّاسٍ ، أَخْبَرَهُ أَنَّ أَبَا سُفْيَانَ أَخْبَرَهُ أَنَّ هِرَقْلَ قَالَ لَهُ سَأَلْتُكَ كَيْفَ كَانَ قِتَالُكُمْ إِيَّاهُ فَزَعَمْتَ أَنَّ الْحَرْبَ سِجَالٌ وَدُوَلٌ، فَكَذَلِكَ الرُّسُلُ تُبْتَلَى ثُمَّ تَكُونُ لَهُمُ الْعَاقِبَةُ .
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.