Question
Why is megillas Esther read twice?
Answer
The Talmud in Tractate Megilla 4a states, in the name of Rabbi Joshua ben Levi, that we read megillas Esther both by day and night. Rashi ad locum comments that the reason for this is in remembrance of the miracle, for in the time of Purim, the Jews cried to God for salvation during the day and night.
Have a Happy Purim!
Shlomo Soroka