"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)." (Using translation from Nasāʾī 3429)  

حَدَّثَنِي ابْنَا قُرَيْظَةَ أَنَّهُمْ عُرِضُوا عَلَى رَسُولِ اللهِ ﷺ يَوْمَ قُرَيْظَةَ «فَمَنْ كَانَ مُحْتَلِمًا أَوْ نَبَتَتْ عَانَتُهُ قُتِلَ وَمَنْ لَمْ يَكُنِ احْتَلَمَ 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." (Using translation from Nasāʾī 3430)  

«كُنْتُ يَوْمَ حَكَمَ سَعْدٌ فِي بَنِي قُرَيْظَةَ غُلَامًا فَشَكُّوا فِيَّ فَلَمْ يَجِدُونِي أَنْبَتُّ فَاسْتُبْقِيتُ فَهَا أَنَا ذَا بَيْنَ أَظْهُرِكُمْ»  

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) when he was fifteen years old, he allowed him. (Using translation from Abū Dāʾūd 2957)  

أَنَّ رَسُولَ اللهِ ﷺ «عَرَضَهُ يَوْمَ أُحُدٍ وَهُوَ ابْنُ أَرْبَعَ عَشْرَةَ فَلَمْ يُجِزْهُ وَعَرَضَهُ يَوْمَ الْخَنْدَقِ وَهُوَ ابْنُ خَمْسَ عَشْرَةَ فَأَجَازَهُ»