Esther 9:26-27

So these days were called Purim, which comes from the word “Pur” (the lot). Because of everything written in this letter and what they had seen and what happened to them, the Jewish people set up this custom. They and their descendants and all those who join them are always to celebrate these two days every year. They should do it in the right way and at the time Mordecai had ordered them in the letter.