Numbers 25:3-5

³And Israel joined himself unto Baal-peor: and the anger of the LORD was kindled against Israel.

⁴And the LORD said unto Moses, Take all the heads of the people, and hang them up before the LORD against the sun, that the fierce anger of the LORD may be turned away from Israel.

⁵And Moses said unto the judges of Israel, Slay ye every one his men that were joined unto Baal-peor.