Nehemiah 13:3

13:3 When they heard the law, they removed from Israel all who were of mixed ancestry.

Nehemiah 13:23-24

13:23 Also in those days I saw the men of Judah who had married women from Ashdod, Ammon, and Moab. 13:24 Half of their children spoke the language of Ashdod (or the language of one of the other peoples mentioned) and were unable to speak the language of Judah.