Esther 9:26-27

26So the Jews call the days of their feast ‘Purim’. That was the name of the dice that Haman used. They did this because of what Mordecai wrote in his letter. They wanted to remember everything that had happened to them.

27They made a rule for all the Jews, their descendants, and any other people who came to join them. The rule said that they must all have a holiday on those two days every year. They must do what Mordecai had written in his letter to them.