From Sahih Bukhari (Hadith 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
Reference: Bukhari 1246