‘Atiyyah Qarazi (may Allah be pleased with him) says: We were presented before the Prophet (peace and blessings of Allah be upon him) on the day of Qurayzah, so whoever had (pubic) hair grown was killed, and whoever did not have it was let go. I was among those who did not have hair, so I was let go. Imam Tirmidhi says:
1- This hadith is hasan sahih,
2- Some people of knowledge act upon this; if puberty and age are not known, they consider the appearance of (pubic) hair as a sign of puberty. This is also the view of Ahmad and Ishaq bin Rahwayh.