Sunan Abi Dawud · Book 20 · Hadith 2957
حَدَّثَنَا أَحْمَدُ بْنُ حَنْبَلٍ، حَدَّثَنَا يَحْيَى، عَنْ عُبَيْدِ اللَّهِ، أَخْبَرَنِي نَافِعٌ، عَنِ ابْنِ عُمَرَ، أَنَّ النَّبِيَّ صلى الله عليه وسلم عُرِضَهُ يَوْمَ أُحُدٍ وَهُوَ ابْنُ أَرْبَعَ عَشْرَةَ فَلَمْ يُجِزْهُ وَعُرِضَهُ يَوْمَ الْخَنْدَقِ وَهُوَ ابْنُ خَمْسَ عَشْرَةَ سَنَةً فَأَجَازَهُ .
Narrated Nafi': That Ibn 'Umar was presented before the Prophet (ﷺ) on the day of Uhud, when he was fourteen years old, but he did not allow him. He was again presented to him on the day of Khandaq (the battle of Trench)…
Sahih