Originally published 3/15/11, 10:11 am.
See The Origin of Ta'anit Esther
The origin of this fast has always been a mystery. A fast on the 13th of Adar is not mentioned in the Megillah. Nor is such a fast mentioned in Tannaitic or Amoraic literature. Megillat Ta'anit, compiled in the first century C.E., includes the 13th of Adar as a day upon which Jews were prohibited from fasting.
A widespread view today is that the fast arose as a post-Talmudic custom intended to commemorate the three days of fasting initiated by Esther in Nissan. There are Rishonim who take this approach. But...
- Mitchell First