Sahih al-Bukhari 1211

It is related from al-Azraq ibn Qays, "We were at al-Ahwaz fighting the al-Haruriyya. While I was on the bank of a river, I saw a man praying holding the reins of his animal in his hand. The animal began to struggle and he began to follow it. (Shu'ba said that the man was Abu Barza al-Aslami.) A man from the Kharijites began to say, 'O Allah! Inflict something on this old man!' When the man finished the prayer, he said, 'I heard what you said. I went on six, seven or eight expeditions with the Messenger of Allah, may Allah bless him and grant him peace, and I saw how he made things easy. I would rather return together with my animal than let it go back to its stable alone which would make things very difficult for me.'" [The Haruriyya are the Kharijites]