Esther 9:27

Overview - Esther 9
1	The Jews slay their enemies, with the ten sons of Haman.
12	Ahasuerus, at the request of Esther, grants another day of slaughter, and Haman's sons to be hanged.
20	The two days of Purim are made festival.

Esther 9:27  (King James Version)
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;