Mujahid (may Allah have mercy on him) said: Sayyiduna Ibn Umar (may Allah be pleased with them both) was present at the Conquest when he was twenty years old. He had with him a stubborn horse and a heavy spear. He said: Abdullah went off to cut fresh grass for his horse, and the Messenger of Allah (peace and blessings be upon him) said: "Where is Abdullah? Where is Abdullah?"
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 9984