פירוש על עבודה זרה 72:8

Perhaps the Torah prohibited a Jewish woman from having sex with a non-Jewish man, for in a patriarchal society she would be drawn into his family. But Jewish men could have sex with non-Jewish women, for these women would be assimilated into Jewish society. Indeed, most Israelite men in the Bible do indeed marry foreign women. Then the later sages prohibited even Jewish men from having sex with non-Jewish women, because after all, this too can frequently lead to assimilation.