“Hashem has called you a verdant olive tree.” (Yirmiyahu 11:16) What made Yirmiyahu compare Bnei Yisroel to an olive tree? All drinkable liquids mix with each other, but oil stands alone. So too, Bnei Yisroel, do not mix with the other nations. As it says (Devarim 7:3) “And you should not be intermarried with them” (Midrash).
The Jewish people are gifted with a very special attribute. Similar to oil which does not mix with water, so too, Bnei Yisroel by virtue of their Divinely inspired nature cannot intermingle with other nations, even if it is their choice to do so. It is for this reason that the Midrash cites the specific posuk of “And you should not be intermarried with them” which is written in the reflexive voice rather than “and do not marry” which is in the active voice. Such a relationship is not only forbidden, but by its very nature cannot succeed and flourish.
