Exodus 34:15 otherwise you might make a covenant with the inhabitants of the land and they would play the harlot with their gods and sacrifice to their gods, and someone might invite you to eat of his sacrifice,

Exodus 34:16 and you might take some of his daughters for your sons, and his daughters might play the harlot with their gods and cause your sons also to play the harlot with their gods.

Joshua 23:12 "For if you ever go back and cling to the rest of these nations, these which remain among you, and intermarry with them, so that you associate with them and they with you,

Ezra 9:2 "For they have taken some of their daughters as wives for themselves and for their sons, so that the holy race has intermingled with the peoples of the lands; indeed, the hands of the princes and the rulers have been foremost in this unfaithfulness." (NASB ©1995)