Numbers 25:1-3

25:1 And Israel abode in Shittim, and the people began to commit whoredom with the daughters of Moab. 25:2 And they called the people unto the sacrifices of their gods: and the people did eat, and bowed down to their gods. 25:3 And Israel joined himself unto Baalpeor: and the anger of the LORD was kindled against Israel.

Numbers 25:5

25:5 And Moses said unto the judges of Israel, Slay ye every one his men that were joined unto Baalpeor.