'Prescribed' in the Bible

the Jewish people established this celebration, making it a tradition for themselves, for their descendants, and for all who joined with them that they should not fail to observe these two days each year, based on the written instructions, and at the prescribed time.

establishing these days of Purim at the prescribed time, just as Mordecai the Jew and Queen Esther had established, and just as the Jewish people had established for themselves and for their descendants. The letter included instructions for their fasting and lamentations.