"13 Moses and Eleazar the priest and all the chiefs of the congregation went to meet them outside the camp. 14 And Moses was angry with the officers of the army, the commanders of thousands and the commanders of hundreds, who had come from service in the war. 15 Moses said to them, “Have you let all the women live? 16 Behold, these, on Balaam's advice, caused the people of Israel to act treacherously against the Lord in the incident of Peor, and so the plague came among the congregation of the Lord. 17 Now therefore, kill every male among the little ones, and kill every woman who has known man by lying with him. 18 But all the young girls who have not known man by lying with him keep alive for yourselves. 19 Encamp outside the camp seven days. Whoever of you has killed any person and whoever has touched any slain, purify yourselves and your captives on the third day and on the seventh day. 20 You shall purify every garment, every article of skin, all work of goats' hair, and every article of wood."
Numbers 31:13-20
The idea that these 'barbarities' took place in primitive times when 'they did not know any better' is at variance with the facts. For it was not the people who initiated this slaughter of 'the innocents' if it had been, we might see the force of such a charge, for the people were a very dubious lot, with much that was unlovely about their character. But it was Moses who remonstrated with the people for not slaying the women and the children. And Moses walked with God. He was the spiritual giant among them, with whom God spoke face to face. Clear- ly, if it had simply been the expression of primitive and savage brutality on the part of a backward people, the story would have read the other way round, with the people slaying the women and children and Moses protesting violently against it. Does not this indicate that there must be something far more in this than at first seems to meet the eye? As for saying they did not know any better, this is simply not true. One has only to think of the legislation we read of in Exodus and in Numbers itself to realise the compassion of God towards women and children, and His special care for them, and for the strangers outwith the covenant (cf Leviticus 19:10, 17, 18; Exodus 23:4, 5; Exodus 22:2123). No, Moses was not acting in a barbarous manner. It is not possible to square his conduct with other Scriptures on this thesis. What he was doing and what he was conscious of doing was that he was acting as a theocratic leader of the people of God, acting as a legal judge in relation to the Midianites, as an executor of divine justice. This is the truth of the position, and some things require to be said about such an idea.