“But now, Oh our God, what can we say after this? For we have disregarded the commands you have through your servants the prophets when you said: ‘The land you are entering to possess is a land polluted by the corruption o the its peoples. By their detestable practices they have filled it with their impurity from one end to the other. Therefore, do not give your daughters in marriage to their sons or take their daughters for your sons. Do not a seek a treaty of friendship with them at any time, that you may be strong and eat the good things of the land and leave it to your children as an everlasting inheritance.'” -Ezra 9:10-12

http://www.alternet.org/world/142478/israeli_government_ads_warn_against_marrying_non-jews_