Deuteronomy 7:2-4

2and when the Lord your God gives them over to you, and you defeat them, then you must devote them to complete destruction. You shall make no covenant with them and show no mercy to them.

3You shall not intermarry with them, giving your daughters to their sons or taking their daughters for your sons,

4for they would turn away your sons from following me, to serve other gods. Then the anger of the Lord would be kindled against you, and he would destroy you quickly.