The Month of Nissan
2. We do not fast during [the month of Nissan] (1). This includes even a
fast on the "Yahrzeit" ("anniversary") [of one's parents' death]. One may,
however, fast because of a disturbing dream ("Ta'anis Chalom") (2). It is
customary for the firstborn to fast on the eve of Pesach, as will be
explained, with God's help, in Chapter 113. A bride and groom should fast
[on the day of their wedding (3), during Nissan]. This applies even on Rosh
Chodesh (4) Nissan.
(1) The month of Nissan is considered a time of joy because it is the
month during which the Israelite nation was liberated from slavery in
Egypt, and during which the "Mishkan" (the mobile "Temple" used while the
Jews were travelling through the desert) was first erected and dedicated.
Consequently, it became customary not to fast during Nissan.
(2) There are various criteria for determining whether one should fast over
a disturbing dream, however, this is not the place to go into the details.
The purpose of a fast is to arouse a person to analyze their life and
repent for any misguided actions and attitudes.
(3) According to the Talmud, one's past transgressions are forgiven on
one's wedding day. Therefore, since it is a personal "Day of Atonement," it
is appropriate to respond to the opportunity through fasting and
repentance. The couple fast until the wedding begins.
(4) In general, not even a bride and groom are allowed to fast on Rosh
Chodesh (first day of the month), however, it is permitted on Rosh Chodesh
Nissan because two of Aaron's sons (Nadav and Avihu) died on that day while
the Jews were travelling in the desert. (Mishna Berura 573:9).