Numbers 25:1-3, 5

Now Israel remained in Acacia Grove, and the people began to commit harlotry with the women of Moab. They invited the people to the sacrifices of their gods, and the people ate and bowed down to their gods. So Israel was joined to Baal of Peor, and the anger of the LORD was aroused against Israel.

So Moses said to the judges of Israel, “Every one of you kill his men who were joined to Baal of Peor.”