All the king's courtiers at the palace gate knelt and bowed low to Haman...but Mordechai would not kneel or bow low (Esther 3:2) ...but Mordechai would not bow low. The literal translation of the phrase is, "but Mordechai will not kneel and will not bow low."
By using the future tense, the verse indicates that in every generation there will arise a spiritual leader who will not kneel and bow to the tyrant of the time. Haman knew that even if he killed Mordechai, another intrepid leader would emerge and take Mordechai's place. That is why Haman wanted to destroy all the Jews in the kingdom.