Deuteronomy 4:46

On this side Jordan, in the valley over against Bethpeor, in the land of Sihon king of the Amorites, who dwelt at Heshbon, whom Moses and the children of Israel smote, after they were come forth out of Egypt: Beth-peor - i:e., house or temple of Peor. It is probable that a temple of this Moabite idol stood in full view of the Hebrew camp while Moses was urging the exclusive claims of God to their worship; and this allusion would be very significant if it were the temple where so many of the Israelites had grievously offended.