Ibn Awn reported,

I wrote to Nafi asking him what kept Ibn Umar back from the military expeditions, and about people who go on a military expedition, do they call the enemy to Islam before fighting them, and may a man within the army charge against the enemy without the permission of his commander?Nafi wrote back to me, "Ibn Umar's sons used to go on military expeditions, and he himself used to provide mounts for warriors. He used to say that the best deed after prayer is jihad in the path of Allah the Exalted. Nothing kept Ibn Umar back from the military expeditions except his duty of carrying out Umar's bequests, his young children, and his many estates. The Messenger of Allah ﷺ launched a surprise attack against Banu Mustaliq while they were heedless, watering their cattle. He killed their fighters and took their women and children captive, and on that day he took Juwayria bint Harith. Ibn Umar narrated this hadith to me, and he was in that army. They used to call the enemy to Islam only in the early days of Islam. As for a man, he must not charge against the enemy formation except with the permission of his commander."

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ابن عون قال

كتبت إلى نافع أسأله ما أقعد ابن عمر رضي الله عنه عن الغزو أو عن القوم إذا غزوا بما يدعون العدو قبل أن يقاتلوهم وهل يحمل الرجل إذا كان في الكتيبة بغير إذن إمامه فكتب إلي إن ابن عمر قد كان يغزو ولده ويحمل على الظهر وكان يقول إن أفضل العمل بعد الصلاة الجهاد في سبيل الله تعالى وما أقعد ابن عمر عن الغزو إلا وصايا لعمر وصبيان صغار وضيعة كثيرة وقد أغار رسول الله ﷺ على بني المصطلق وهم غارون يسقون على نعمهم فقتل مقاتلتهم وسبى سباياهم وأصاب جويرية بنت الحارث قال فحدثني بهذا الحديث ابن عمر وكان في ذلك الجيش وإنما كانوا يدعون في أول الإسلام وأما الرجل فلا يحمل على الكتيبة إلا بإذن إمامه