Sahih al-Bukhari 1246
Narrated Anas bin Malik:
The Prophet (ﷺ) said, "Zaid took over the flag and was martyred. Then it was taken by Jafar who was 
martyred as well. Then `Abdullah bin Rawaha took the flag but he too was martyred and at that time 
the eyes of Allah's Messenger (ﷺ) were full of tears. Then Khalid bin Al-Walid took the flag without being 
nominated as a chief (before hand) and was blessed with victory."
حَدَّثَنَا أَبُو مَعْمَرٍ، حَدَّثَنَا عَبْدُ الْوَارِثِ، حَدَّثَنَا أَيُّوبُ، عَنْ حُمَيْدِ بْنِ هِلاَلٍ، عَنْ أَنَسِ بْنِ مَالِكٍ ـ رضى الله عنه ـ قَالَ قَالَ النَّبِيُّ صلى الله عليه وسلم ‏
"‏ أَخَذَ الرَّايَةَ زَيْدٌ فَأُصِيبَ، ثُمَّ أَخَذَهَا جَعْفَرٌ فَأُصِيبَ، ثُمَّ أَخَذَهَا عَبْدُ اللَّهِ بْنُ رَوَاحَةَ فَأُصِيبَ ـ وَإِنَّ عَيْنَىْ رَسُولِ اللَّهِ صلى الله عليه وسلم لَتَذْرِفَانِ ـ ثُمَّ أَخَذَهَا خَالِدُ بْنُ الْوَلِيدِ مِنْ غَيْرِ إِمْرَةٍ فَفُتِحَ لَهُ ‏"‏