Esther 9:26-28

So these days were named Purim, after the name of Pur. And so, because of the words of this letter, and of what they had seen in connection with this business, and what had come to them, The Jews made a rule and gave an undertaking, causing their seed and all those who were joined to them to do the same, so that it might be in force for ever, that they would keep those two days, as ordered in the letter, at the fixed time every year; And that those days were to be kept in memory through every generation and every family, in every division of the kingdom and every town, that there might never be a time when these days of Purim would not be kept among the Jews, or when the memory of them would go from the minds of their seed.