Numbers 25:3-5

³And Israel joined himself unto the Baal of Peor; and the anger of the LORD was kindled against Israel.

⁴And the LORD said unto Moses: 'Take all the chiefs of the people, and hang them up unto the LORD in face of the sun, that the fierce anger of the LORD may turn away from Israel.'

⁵And Moses said unto the judges of Israel: 'Slay ye every one his men that have joined themselves unto the Baal of Peor.'