Numbers 25:1-3

Israel settled and remained in Shittim, and the people began to play the prostitute with the women of Moab [by being unfaithful to God]. For they invited the Israelites to the sacrifices of their gods, and the Israelites ate [food offered to idols] and bowed down to Moab’s gods. So Israel joined themselves to Baal of Peor [in worship]. And the anger of the LORD was kindled against Israel.