"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."
Sunan an-Nasa'i Book 27, Hadith 42
← Previous Hadith "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)."

Sunan an-Nasa'i Book 27, Hadith 41 Next Hadith → 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).

Sunan an-Nasa'i Book 27, Hadith 43