בְּיוֹם־שְׁלֹשָׁ֥ה עָשָׂ֖ר לְחֹ֣דֶשׁ אֲדָ֑ר וְנ֗וֹחַ בְּאַרְבָּעָ֤ה עָשָׂר֙ בּ֔וֹ וְעָשֹׂ֣ה אֹת֔וֹ י֖וֹם מִשְׁתֶּ֥ה וְשִׂמְחָֽה׃
on the thirteenth day of the month Adar, and on the fourteenth day of the same they rested, and made it a day of feasting and gladness.
Read kabbalistic (mystical) interpretation of Esther 9:17: and classical mystical sources.