A common misinterpretation views this verse as Mordecai instituting a new binding religious law or scripture equivalent to the Torah, when it actually refers to his administrative letter coordinating the festival's celebration based on prior communal vows; others mistakenly limit Purim to mere feasting without recognizing its roots in fasting and lamentation over the threatened genocide, or assume the inclusion of 'those who joined themselves unto their fasts' mandates non-Jews to convert formally, whereas it simply acknowledges sympathetic participants honoring the event without altering Jewish covenantal boundaries.
Esther 9:31
King James Version (1769)
31 To confirm these days of Purim in their times appointed, according as Mordecai the Jew and Esther the queen had enjoined them, and as they had decreed for themselves and for their seed, the matters of the fastings and their cry.
This passage describes the formal establishment of the Purim festival among the Jewish people, confirming its observance at the designated times as prescribed by Mordecai's letter and the voluntary commitments made by the community, their descendants, and even proselytes who participated in the fasts and prayers during the crisis; it underscores themes of communal remembrance, deliverance from destruction, and the enduring legacy of God's providence through human leadership in preserving Jewish identity and traditions.