Ibn Awn says: I wrote a letter to Nafi' to ask whether it is necessary to give an invitation (to Islam) before fighting. So he wrote back to me that this command was in the beginning of Islam. When the Messenger of Allah (peace be upon him) attacked Banu Mustaliq, they were completely unaware and their cattle were drinking water. He killed them, took their women and children captive, and Juwayriya bint al-Harith (may Allah be pleased with her) was among those captives. This hadith was narrated to me by Abdullah ibn Umar (may Allah be pleased with them both), who himself was part of that army.