This Bible contradiction is from the Skeptic's Annotated Bible.

Verses

Yes.

Numbers 31:7 View context

And they warred against the Midianites, as the LORD commanded Moses; and they slew all the males.

Numbers 31:16-17 View context

Behold, these caused the children of Israel, through the counsel of Balaam, to commit trespass against the LORD in the matter of Peor, and there was a plague among the congregation of the LORD.

Now therefore kill every male among the little ones, and kill every woman that hath known man by lying with him.

No.

Judges 6:1-2 View context

And the children of Israel did evil in the sight of the LORD: and the LORD delivered them into the hand of Midian seven years.

And the hand of Midian prevailed against Israel: [and] because of the Midianites the children of Israel made them the dens which [are] in the mountains, and caves, and strong holds.

Judges 6:5 View context

For they came up with their cattle and their tents, and they came as grasshoppers for multitude; [for] both they and their camels were without number: and they entered into the land to destroy it.