Judges 21:1-14 The men of Israel had taken an oath at Mizpah: “Not one of us will give his daughter in marriage to a Benjamite.”
The people went to Bethel, where they sat before God until evening, raising their voices and weeping bitterly. “O LORD, the God of Israel,” they cried, “why has this happened to Israel? Why should one tribe be missing from Israel today?”
Early the next day the people built an altar and presented burnt offerings and fellowship offerings.
Then the Israelites asked, “Who from all the tribes of Israel has failed to assemble before the LORD ?” For they had taken a solemn oath that anyone who failed to assemble before the LORD at Mizpah should certainly be put to death.
Now the Israelites grieved for their brothers, the Benjamites. “Today one tribe is cut off from Israel,” they said. “How can we provide wives for those who are left, since we have taken an oath by the LORD not to give them any of our daughters in marriage?” Then they asked, “Which one of the tribes of Israel failed to assemble before the LORD at Mizpah?” They discovered that no one from Jabesh Gilead had come to the camp for the assembly. For when they counted the people, they found that none of the people of Jabesh Gilead were there.
So the assembly sent twelve thousand fighting men with instructions to go to Jabesh Gilead and put to the sword those living there, including the women and children. “This is what you are to do,” they said. “Kill every male and every woman who is not a virgin.” They found among the people living in Jabesh Gilead four hundred young women who had never slept with a man, and they took them to the camp at Shiloh in Canaan.
Then the whole assembly sent an offer of peace to the Benjamites at the rock of Rimmon. So the Benjamites returned at that time and were given the women of Jabesh Gilead who had been spared. But there were not enough for all of them.
This breaks down the theory that God kills everyone (including babies) to keep evil from spreading.