"The sons of Quraizah told me that they were presented to the Messenger of Allah on the Day of Quraizah, and whoever (among them) had reached puberty, or had grown pubic hair, was killed, and whoever had not reached puberty and had not grown pubic hair was left (alive)."  

حَدَّثَنِي أَبْنَاءُ قُرَيْظَةَ أَنَّهُمْ عُرِضُوا عَلَى رَسُولِ اللَّهِ ﷺ يَوْمَ قُرَيْظَةَ فَمَنْ كَانَ مُحْتَلِمًا أَوْ نَبَتَتْ عَانَتُهُ قُتِلَ وَمَنْ لَمْ يَكُنْ مُحْتَلِمًا أَوْ لَمْ تَنْبُتْ عَانَتُهُ تُرِكَ  

"On the day that Sa'd passed judgment on Banu Quraizah I was a young boy and they were not sure about me, but they did not find any pubic hair, so they let me live, and here I am among you."  

كُنْتُ يَوْمَ حُكْمِ سَعْدٍ فِي بَنِي قُرَيْظَةَ غُلاَمًا فَشَكُّوا فِيَّ فَلَمْ يَجِدُونِي أَنْبَتُّ فَاسْتُبْقِيتُ فَهَا أَنَا ذَا بَيْنَ أَظْهُرِكُمْ  

It was narrated from Ibn 'Umar that he presented himself to the Messenger of Allah on the Day of Uhud when he was fourteen years old, but he did not permit him (to join the army). He presented himself on the Day of Al-Khandaq when he was fifteen years old, and he permitted him (to join the army).  

أَنَّ رَسُولَ اللَّهِ ﷺ عَرَضَهُ يَوْمَ أُحُدٍ وَهُوَ ابْنُ أَرْبَعَ عَشْرَةَ سَنَةً فَلَمْ يُجِزْهُ وَعَرَضَهُ يَوْمَ الْخَنْدَقِ وَهُوَ ابْنُ خَمْسَ عَشْرَةَ سَنَةً فَأَجَازَهُ