Sahih Muslim 1868
Sahih Muslim · Book 33: The Book on Government · The age of responsibility
This tradition has been handed down through a different chain Of transmitters with the following change in the wording:
وَحَدَّثَنَاهُ أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ ، حَدَّثَنَا عَبْدُ اللَّهِ بْنُ إِدْرِيسَ ، وَعَبْدُ الرَّحِيمِ بْنُ، سُلَيْمَانَ ح وَحَدَّثَنَا مُحَمَّدُ بْنُ الْمُثَنَّى ، حَدَّثَنَا عَبْدُ الْوَهَّابِ، - يَعْنِي الثَّقَفِيَّ - جَمِيعًا عَنْ عُبَيْدِ، اللَّهِ بِهَذَا الإِسْنَادِ غَيْرَ أَنَّ فِي حَدِيثِهِمْ وَأَنَا ابْنُ أَرْبَعَ عَشْرَةَ سَنَةً فَاسْتَصْغَرَنِي .
" I was fourteen years old and he thought me too young (to participate in the fight)."