Musannaf Ibn Abi Shaybah 35950 — Taking boys on campaign, and those

Sayyiduna Ibn Umar (may Allah be pleased with them both) said: On the day of the Battle of Uhud I was presented before the Messenger of Allah (peace and blessings be upon him) to take part in jihad. At that time I was fourteen years old. I was considered too young and was sent back. Then on the day of the Battle of the Trench I was presented, and at that time I was fifteen years old, and I was given permission. Nafi' said: I narrated this report to Umar bin Abd al-Aziz when he was caliph, and he said: "This is indeed a limit between the young and the grown." He then wrote to his governors: "Whoever has reached the age of fifteen, assign him to jihad, and whoever is younger than that, assign him among the family and dependants."