Mujahid (may Allah have mercy on him) says that Sayyiduna Ibn Umar (may Allah be pleased with them both) was present at the time of the conquest of Makkah. At that time, he was twenty years old. He had a steadfast horse and a heavy spear with him. He went and started cutting grass for his horse. The Noble Prophet (peace and blessings of Allah be upon him) called out to him repeatedly to stop him.