Musnad Ahmad Hadith 4873

Ibn Awn says that once I wrote a letter and asked Nafi’ (may Allah have mercy on him) why Ibn Umar (may Allah be pleased with them both) had stopped participating in jihad, while before the battle began he used to pray for it, and whether any person could attack an army without the permission of his leader? He replied to me in writing that Ibn Umar (may Allah be pleased with them both) participated in every jihad and rode on the back of an animal, and he himself used to say that after prayer, the most virtuous deed is jihad in the way of Allah. Now, Ibn Umar (may Allah be pleased with them both) not participating in jihad is due to being occupied in fulfilling some bequests of Umar (may Allah be pleased with him), taking care of small children, and managing much land. And the Noble Prophet (ﷺ) attacked Banu Mustaliq at a time when they were heedless and watering their animals. The Noble Prophet (ﷺ) had their fighting men killed, their women taken captive, and Lady Juwayriya (may Allah be pleased with her) came into the share of the Noble Prophet (ﷺ). This hadith was narrated to me by Ibn Umar (may Allah be pleased with them both), who participated in that army, and those people used to first invite to Islam. As for the rest, no person can attack any army without the permission of his leader.