The Fast of Esther (Taanit Esther or “Esther Fast”) is a dawn-to-nightfall fast held on the day before the holiday of Purim. The festival of Purim commemorates the Divinely orchestrated salvation of the Jewish people in the ancient Persian Empire from Haman’s plot “to destroy, kill and annihilate all the Jews, young and old, infants and women, in a single day.” These events are recorded in the Book of Esther, and the salvation that came about at that time is celebrated on the holiday of Purim ( the Jewish holiday, not feast, that commemorates the Jews’ salvation from Haman’s plot to annihilate them).
Esther Learns of Haman’s Plot – Esther 4:12-17 NASB1995
“12 They related Esther’s words to Mordecai.
13 Then Mordecai told them to reply to Esther, “Do not imagine that you in the king’s palace can escape any more than all the Jews. 14 For if you remain silent at this time, relief and deliverance will arise for the Jews from another place and you and your father’s house will perish. And who knows whether you have not attained royalty for such a time as this?”
Esther Plans to Intercede
15 Then Esther told them to reply to Mordecai, 16 “Go, assemble all the Jews who are found in Susa, and fast for me; do not eat or drink for three days, night or day. I and my maidens also will fast in the same way. And thus I will go in to the king, which is not according to the law; and if I perish, I perish.” 17 So Mordecai went away and did just as Esther had commanded him.” – Esther 4:12-17 NASB1995