Esther 4:8 (ESV)

8 Mordecai also gave him a copy of the written decree issued in Susa for their destruction, that he might show it to Esther and explain it to her and command her to go to the king to beg his favor and plead with him on behalf of her people.

In order to prove this almost inconceivable course of events, Mordecai handed a copy of the edict to Hathach, to show to Esther. Then he unfolded his plan for the rescue of the Jews. At Esther’s entry into the king’s harem, Mordecai had forbidden her to reveal her nationality. Now, however, he asked her to reveal her Jewish identity to the king and to plead with him for her people. Such a step would be very dangerous to Esther herself. Clearly, Mordecai thought that she was the Jews’ only hope of survival.