From Sahih Bukhari (Hadith 4024):
Narrated Said bin Al-Musaiyab: When the first civil strife (in Islam) took place because of the murder of 'Uthman, it left none of the Badr warriors alive. When the second civil strife, that is the battle of Al-Harra, took place, it left none of the Hudaibiya treaty companions alive. Then the third civil strife took place and it did not subside till it had exhausted all the strength of the people
Reference: Bukhari 4024