Nehemiah 10:30
That way we would not give our daughters to the peoples of the lands, or take their daughters for our sons;
Exodus 34:16
You might take some of his daughters for your sons, and his daughters might commit spiritual immorality (fornication) with their gods and cause your sons also to commit spiritual immorality with their gods.
Deuteronomy 7:3
Do not intermarry with them. Do not give your daughters to their sons or take their daughters for your sons.
Ezra 9:1-3
After these things were done, the captains came to me and said: The people of Israel and the priests and Levites have not kept themselves separate from the people of the lands. They have taken part in the disgusting ways of the Canaanites, the Hittites, the Perizzites, the Jebusites, the Ammonites, the Moabites, the Egyptians, and the Amorites.
Ezra 9:12-14
Do not give your daughters to their sons or take their daughters for your sons or do anything for their peace or well being for a very long time. That way you may be strong, living on the good of the land, and handing it on to your children for a heritage for as long as they live.
Ezra 10:10-12
Ezra the priest got to his feet and said to them: You have done wrong and taken strange women for your wives, thus increasing the sin of Israel.