Deuteronomy 7:2-4

2and when Jehovah thy 1God shall give them up before thee and thou shalt smite them, then shalt thou utterly destroy them: thou shalt make no covenant with them, nor shew mercy unto them.

3And thou shalt make no marriages with them: thy daughter thou shalt not give unto his son, nor take his daughter for thy son;

4for he will turn away thy son from following me, and they will serve other 2gods, and the anger of Jehovah will be kindled against you, and he will destroy thee quickly.