וַיִּשְׁלַ֤ח סְפָרִים֙ אֶל־כָּל־מְדִינ֣וֹת הַמֶּ֔לֶךְ אֶל־מְדִינָ֤ה וּמְדִינָה֙ כִּכְתָבָ֔הּ וְאֶל־עַ֥ם וָעָ֖ם כִּלְשׁוֹנ֑וֹ לִהְי֤וֹת כָּל־אִישׁ֙ שֹׂרֵ֣ר בְּבֵית֔וֹ וּמְדַבֵּ֖ר כִּלְשׁ֥וֹן עַמּֽוֹ׃ (פ)
Rashi on Esther
And his people’s language be the one spoken. He can compel his wife to learn his language if her native tongue is different.33Ibid. 4:12. The purpose for this law was to make wives show respect and subjugation to their husbands.