It was narrated that Ibn`Umar said:
“I was presented to the Messenger of Allah ﷺ on the day of Uhud, when I was fourteen years old, but he did not permit me (to fight). I was presented to him on the Day of Khandaq when I was fifteen years old, and he permitted me (to fight).' ”

حَدَّثَنَا عَلِيُّ بْنُ مُحَمَّدٍ، حَدَّثَنَا عَبْدُ اللَّهِ بْنُ نُمَيْرٍ، وَأَبُو مُعَاوِيَةَ وَأَبُو أُسَامَةَ قَالُوا حَدَّثَنَا عُبَيْدُ اللَّهِ بْنُ عُمَرَ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، قَالَ عُرِضْتُ عَلَى رَسُولِ اللَّهِ ﷺ يَوْمَ أُحُدٍ وَأَنَا ابْنُ أَرْبَعَ عَشْرَةَ سَنَةً فَلَمْ يُجِزْنِي وَعُرِضْتُ عَلَيْهِ يَوْمَ الْخَنْدَقِ وَأَنَا ابْنُ خَمْسَ عَشْرَةَ سَنَةً فَأَجَازَنِي . قَالَ نَافِعٌ فَحَدَّثْتُ بِهِ عُمَرَ بْنَ عَبْدِ الْعَزِيزِ فِي خِلاَفَتِهِ فَقَالَ هَذَا فَصْلُ مَا بَيْنَ الصَّغِيرِ وَالْكَبِيرِ .