Abdullah bin Umar (may Allah be pleased with them both) narrated that on the occasion of the Battle of Uhud, he presented himself before the Messenger of Allah (peace and blessings of Allah be upon him) to participate in the battle, but he was not granted permission. At that time, he was fourteen years old. Then, on the occasion of the Battle of Khandaq, he presented himself again and was granted permission. At that time, he was fifteen years old.