The answer is: Put on sackcloth and ashes

Esther 4:1

When Mordecai discovered Haman's horrifying plot to annihilate the Jewish people, his response was a somber yet symbolic act of mourning: he donned sackcloth and ashes. This attire, commonly associated with grief and repentance in ancient cultures, illustrated his deep anguish. You can almost picture him sitting in the public square—disheveled and distraught—drawing attention with this powerful display of sorrow. Expertly signaling that something monumental was amiss.

But here's a fun tidbit: where there’s worry, there's also the chance for great ingenuity! This dramatic act was not just about individual mourning; it eventually prompted Esther, Mordecai's cousin, to reveal her own Jewish identity and take daring steps to save her people. In a twist of divine irony, while Haman sought to elevate himself through the humiliation of the Jews, it was Mordecai’s sincere distress that ushered in a turning point for Israel.

The use of sackcloth can be traced back through Hebrew Scriptures, reflecting a rich tradition. It echoed the lamentations in books like Jonah, where the whole city of Nineveh donned sackcloth in repentance when faced with impending doom.

In this story of courage and identity, we see the intertwined destinies of two Jewish figures facing overwhelming odds. It highlights the strength found in community, resilience, and, of course, the power of standing up for what is just—even in the face of peril.