There
is a rabbinical fast, called the The
Fast of the Firstborn, which occurs on the day before Pesah,
Passover, which precedes the Hag Hamatzot – festival of Matzot.
This
fast is without basis in the Torah, but in fact goes against the
entire spirit of the Torah, if not the Law itself. The purported
purpose is to show gratitude for the Firstborn of Israel, who were
not slaughtered along with the Egyptians, on the night of the 10th
plague.
A
summary is given here:
https://en.wikipedia.org/wiki/Fast_of_the_Firstborn
First
and foremost, there is no existence of such a fast in the Torah. It
is entirely of rabbinical imagination, conception, and production.
However, the details of the Torah on the actual plague suggest that
it is contrary to the entire purpose of the Plagues, especially the
10th.
In
Exodus we see an explanation of the plague and what it symbolizes for
israel:
Ex
11:
7
But against any of the children of Israel shall not a dog whet his
tongue, against man or beast; that ye may know how that the LORD doth
put a difference between the Egyptians and Israel.
And
9
And the LORD said unto Moses: 'Pharaoh will not hearken unto you;
that My wonders may be multiplied in the land of Egypt.'
So
this explanation is about the wonders carried out for Israel, and do
not require a fast or any kind of guilt.
It
could be argued that the blood of the Paschal lamb is symbolised by
this fast, thus in Ex 12:
13
And the blood shall be to you for a token upon the houses where ye
are; and when I see the blood, I will pass over you, and there shall
no plague be upon you to destroy you, when I smite the land of Egypt.
But
this is a practical part of the Paschal lamb, which technically we
are still required to fulfill these days as well. It is not about a
fast, but a remembrance. The following verse is also pertinent:
14
And this day shall be unto you for a memorial, and ye shall keep it a
feast to the LORD; throughout your generations ye shall keep it a
feast by an ordinance for ever.
The
very day (14th
of the first month) is a Feast for every generation. Furthermore,
we are meant to celebrate the wonders that God has bestowed upon us,
not to mourn and feel regret for them. Thsi Catholic attitude of
guilt is carried through to the Passover seder , where 10 drops of
wine are spilt in commemoration and mourning for the 10 plagues. The
very miracles for which we celebrate and have festivals ordained for
us, are stealthily turned into objects of mourning, guilt and self
flagellation. This attitude, whether by rabbinic or Karaites is
totally false and part of the destructive nature of man made
religion.