Verses 15-18:15 “Have you allowed all the women to live?” he asked them. 16 “They were the ones who followed Balaam’s advice and enticed the Israelites to be unfaithful to the Lord in the Peor incident, so that a plague struck the Lord’s people. 17 Now kill all the boys. And kill every woman who has slept with a man, 18 but save for yourselves every girl who has never slept with a man."
Numbers 31:1 - 51
MSG - 1 God spoke to Moses: "Avenge the People of Israel on the Midianites. Afterward you will go to be with your dead ancestors. 3 Moses addressed the people: "Recruit men for a campaign against Midian, to exact God's vengeance on Midian, a thousand from each tribe of Israel to go to war.
For follow-up discussion and general commentary on the topic. Comments are sorted chronologically.
Things were weird back in the days in Numbers 31. There was a difference of rape and fornication. The men would have sexual intercourse with the young girls (seems young girls married earlier than today and were young) and they could tell if a young girl would have pain and yelled out after penetration whether she was a virgin or not if she was not a virgin. He would have to marry her if she was a virgin or kill her if she was not. You have to look at the spoiles that were taken and their customs and culture aspect
concerning the subject. Again I have to say that it was weird back then. The Bible just says that the virgins were young and does not mention the age, but as was the custom back then, any man could have as many as he could afford. Maybe some one else can bring more light into this picture of Numbers 31.
I heard it mentioned recently that Hebrew is a language of what "should be", rather than always what is. As such, to say a 'girl who has never slept with a man' is equivalent (in Hebrew) to saying she was a an unmarried girl, and 'young girl' is equivalent to virgin - for young unmarried women were to be virgins.
As such, they would have killed the wives (who had enticed the Israelites to adultery and idolatry - Num 25:1-3), or any obvious prostitute, but saved the younger women. They did not actually have to test each girl to see if she was a virgin, though as Tony said those taken as wives would have been killed if it was found out they were not. It is likely many of these women became servants, as was practice for captives taken in war by Israel or other nations of the time (II Kings 5:2, I Kings 1:21).
Deut 21:10-14
The spoils of war were allotted to the soldiers, priests, and distributed among the community, it was not a system of who could buy the most (thoguh I assume people could sell to each other). Men were allowed to have multiple wives + further wives without inheritance rights (sometimes referred to as concubines in the Bible), though the usual number from examples in scripture seems to be 1-5 or so. Solomon multiplied wives to the extreme, but that was not particularly a good thing (Deut 17:6), nor was it common.