Numbers 25:16-18 - Vengeance Against The Midianites
16 And the LORD spoke to Moses, saying, 17 "Harass the Midianites and strike them down, 18 for they have harassed you with their wiles, with which they beguiled you in the matter of Peor, and in the matter of Cozbi, the daughter of the chief of Midian, their sister, who was killed on the day of the plague on account of Peor."