Esther 9:25 (KJV)

And the Jews undertook to do as they had begun, and as Mordecai had written unto them;

Because Haman the son of Hammedatha, the Agagite, the enemy of all the Jews, had devised against the Jews to destroy them, and had cast Pur, that is, the lot, to consume them, and to destroy them;

But when Esther came before the king, he commanded by letters that his wicked device, which he devised against the Jews, should return upon his own head, and that he and his sons should be hanged on the gallows.

Wherefore they called these days Purim after the name of Pur. Therefore for all the words of this letter, and of that which they had seen concerning this matter, and which had come unto them,

The Jews ordained, and took upon them, and upon their seed, and upon all such as joined themselves unto them, so as it should not fail, that they would keep these two days according to their writing, and according to their appointed time every year;