Kommentar zu Esther 4:17

Mordechai passed. [I.e., he transgressed] the law⁹Otherwise, ויעבר מרדכי is apparently superfluous because the text further states that he implemented all her instructions. Alternatively, Mordechai actually went over (=ויעבר) a bridge. (Maseches Megillah 15a) by fasting on the first festive day of Pesach, for he fasted on the fourteenth, the fifteenth¹⁰I.e., Pesach. Although the holiday feast is obligatory, Mordechai bypassed the obligation and ordered the fast, using the special authority of the Sanhedrin to suspend such obligations in times of extreme need. (Maseches Megillah 15a) ,¹¹Midrash Esther Rabbah (8:7) is of the opinion that the three day fast was on the thirteenth, fourteenth and fifteenth day of Nisan. and the sixteenth, for the letters were written on the thirteenth day.