Sahih al-Bukhari 3721
Narrated `Urwa:
On the day of the battle of Al-Yarmuk, the companions of the Prophet (ﷺ) said to Az-Zubair, "Will you 
attack the enemy vigorously so that we may attack them along with you?" So Az-Zubair attacked 
them, and they inflicted two wounds over his shoulder, and in between these two wounds there was an 
old scar he had received on the day of the battle of Badr When I was a child, I used to insert my 
fingers into those scars in play.
حَدَّثَنَا عَلِيُّ بْنُ حَفْصٍ، حَدَّثَنَا ابْنُ الْمُبَارَكِ، أَخْبَرَنَا هِشَامُ بْنُ عُرْوَةَ، عَنْ أَبِيهِ، أَنَّ أَصْحَابَ النَّبِيِّ، صلى الله عليه وسلم قَالُوا لِلزُّبَيْرِ يَوْمَ الْيَرْمُوكِ أَلاَ تَشُدُّ فَنَشُدَّ مَعَكَ فَحَمَلَ عَلَيْهِمْ، فَضَرَبُوهُ ضَرْبَتَيْنِ عَلَى عَاتِقِهِ، بَيْنَهُمَا ضَرْبَةٌ ضُرِبَهَا يَوْمَ بَدْرٍ‏.‏ قَالَ عُرْوَةُ فَكُنْتُ أُدْخِلُ أَصَابِعِي فِي تِلْكَ الضَّرَبَاتِ أَلْعَبُ وَأَنَا صَغِيرٌ‏.‏