EXO 34:15

15 Do not make peace agreements with [any group] that lives in that land. When they worship their gods and offer sacrifices to their gods, and they invite you to join them, do not join them. If [you join them], you will eat the food that they sacrifice to their gods, and [you will not be faithful to me. You will be like people who] commit adultery, [who are not being faithful to their spouses] [MET].