Laws of the Megillah
5. Just before Purim, it is customary to donate the value of half of the
standard monetary unit currently in use in one's local region (1), as a
remembrance of the half-shekel ("Machtzis HaShekel") that people [were
obligated] to donate [to the Beit Hamikdash (Temple)] every Adar for the
purchase of the [animals used for the] communal sacrifices (2). It has
become customary to donate three times the value of half [of the standard
monetary unit], because in Parashas Ki Sisa (Exodus 30:11), it says the
word "Terumah" ("donation") three times [in the paragraph discussing the
mitzvah to donate the half-shekel].
The money should be given in the evening, before the Megillah reading. It
should be distributed to the poor. A minor is exempt from this donation,
but if his father contributes on his behalf one time, it becomes his
obligation for life. According to some authorities, a thirteen year old boy
is obligated to donate, while others rule that he is exempt until the age
(1) A half of a dollar in the United States.
(2) From Rosh Chodesh Nissan onwards, the animals used for all the communal
sacrifices had to be purchased using money collected that year. Therefore,
one month before, on Rosh Chodesh Adar, announcements would be made to
remind people to donate the half-shekel, so that animals could be purchased
with the "new" money before Nissan. The reading of Parashas Shekalim just
before (or on) Rosh Chodesh Adar also serves as a reminder of that mitzvah
(See HY 140:1).