Prescribed Punishments (Kitab Al-Hudud)
Dawud :: Book 38 : Hadith 4390
Narrated Atiyyah al-Qurazi:
I was among the captives of Banu Qurayzah. They (the Companions) examined us, and those who had begun to grow hair (pubes) were killed, and those who had not were not killed. I was among those who had not grown hair.