21 charging them to observe the fourteenth and fifteenth days of Adar, every year—
l’-ka-YAYM a-lay-HEM lih-YOT o-SEEM AYT YOM ar-ba-AH a-SAR l’-KHO-desh a-DAR v’-AYT yom kha-mi-SHAH a-SAR BO b’-khol sha-NAH v’-sha-NAH
כא לְקַיֵּם עֲלֵיהֶם לִהְיוֹת עֹשִׂים אֵת יוֹם אַרְבָּעָה עָשָׂר לְחֹדֶשׁ אֲדָר וְאֵת יוֹם־חֲמִשָּׁה עָשָׂר בּוֹ בְּכָל־שָׁנָה וְשָׁנָה׃
9:21 To observe the fourteenth and fifteenth days of Adar
Purim is the only Jewish holiday that is observed on two different days, depending on one’s location. The residents of cities that were walled at the time that the Jewish people entered the Land of Israel with Yehoshua celebrate on the fifteenth of Adar, while the rest of the world celebrates on the fourteenth. Pracitically, the only city that celebrates Purim on the fifteenth of Adar is Yerushalayim. In establishing the holiday of Purim, Esther wanted to guarantee that the lesson of Purim would not be forgotten. In her time, the Children of Israel had forsaken Yerushalayim when they feasted at a party celebrating its destruction. Celebrating in Yerushalayim on a different day highlights its special status and its eternal connection to the People of Israel.