There are several interesting  parallels in the Final Meal before the Fast of Tisha b’Av and Yom Kippur
-  The most  obvious parallel  is that both fasts are for a  full day - actually about 25 hours - as opposed to other fasts which are  from early morning until night.
- Both Final Meals traditionally follow the Minchah  Service.
- Both Final Meals have several custsoms and rituals  that are unique to these meals.
 
What makes these meals so special?  Nearly every Holiday has a special ritual at mealtime. The most  obvious is the Passover Seder.  At New Year, we  eat special symbolic foods to start the year off right.  At  Sukkoss we eat in the Sukkah and even Shavuous we have the custom of  eating dairy.
 
The problem with eating on Yom Kippur and Tisha b’Av is obvious  since that they are both Fast Days.  And since  they are both FULL DAY fasts, we cannot possibly engineer a meal that  would symbolize the day. That is where the final meal comes in.  The  reason it is eaten after Minchah is to connect as closely as possible  it to the upcoming fast day.  This  explains perhaps why we specifcally recite the confession at Minchah  BEFORE the meal on Yom Kippur eve.   Since Yom Kippur is after all a Yom Tov, this final meal is  somewhat festive.  We have Challah, some have  honey and we eat meat - although it is wise to eat bland and easily  digested foods to prepare for the fast.
 
On the other hand, Tisha b’Av is a day of mourning. Mourners  coming back from the burial normally DO have a special Mourner’s Meal.  Since we cannot eat on Tisha b’Av, this mourners meal  takes place BEFORE the Fast.
 
Therefore, these Final Meals before Both fast, function as  substitutes for the meals that should have been consumed on the days  themselves, but could not due to the fasts.     
 
The Talmud teaches us that whoever  eats on Yom Kippur Eve for the sake of the Yom Kippur Fast Day is  considered to have fasted Both Days.
KT
RRW
Preriously Published On NishmaBlog  - Thursday, September 6, 2007