Mukhtasar Bukhari

It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that the Noble Prophet (peace and blessings be upon him) called him before himself on the day of the Battle of Uhud, and at that time he was fourteen years old. (He says that) the Prophet (peace and blessings be upon him) did not permit me. After that, on the day of Khandaq, he called me before himself, and at that time I was fifteen years old, so the Prophet (peace and blessings be upon him) permitted me.