Sahih al-Bukhari 3975

Narrated `Urwa:On the day of (the battle) of Al-Yarmuk, the companions of Allah's Messenger (ﷺ) said to Az-Zubair, "Will you attack the enemy so that we shall attack them with you?" Az-Zubair replied, "If I attack them, you people would not support me." They said, "No, we will support you." So Az-Zubair attacked them (i.e. Byzantine) and pierced through their lines, and went beyond them and none of his companions was with him. Then he returned and the enemy got hold of the bridle of his (horse) and struck him two blows (with the sword) on his shoulder. Between these two wounds there was a scar caused by a blow, he had received on the day of Badr (battle). When I was a child I used to play with those scars by putting my fingers in them. On that day (my brother) "Abdullah bin Az-Zubair was also with him and he was ten years old. Az-Zubair had carried him on a horse and let him to the care of some men.