The Search and Nullification of Chometz
1. One should search for "chometz" (1) on the night before Erev Pesach
(that is, the night of the 14th of Nissan) (2). We are obligated to
conduct the search at the beginning of the night (3). One should not eat
(4), nor perform any work, from a half hour before nightfall onward [until
he finishes the search].
(1) "Chometz results when one of the five species of grain - wheat,
barley, rye, oats, and spelt, or one of their derivatives - is allowed to
remain undisturbed in contact with water for 18 minutes or more. Chometz
results instantly when these grains are exposed to hot or salted water."
("Laws of Pesach" by Rabbi Blumenkrantz). Foods like bread, cake, cereals,
noodles, whiskey and beer are Chometz.
(2) Based on a verse in the Torah (Exodus 12:15), on the morning of the
14th of Nissan, before Midday, there is a mitzvah to mentally view all
Chometz in one's possession as owner-less ("hefker") and as useless as
dirt. This activity is called "Hashbasah" (or "Bitul") and if done
correctly, with full mental commitment, will prevent one from violating
the prohibition to possess Chometz on Pesach (we articulate this mental
commitment verbally). However, the Sages were concerned that not everyone
would be able to perform the "bitul" with full mental commitment, and
therefore, they ruled that in addition to mental bitul, we are all
obligated to search ("bedikah") for the Chometz in our possession, and to
dispose ("biur") of what we find (Mishna Berura 431:2). As we shall see in
Chapter 14, one can sell his chometz to a Gentile before Pesach.
(3) Immediately after the appearance of three stars (Mishna Berura 431:1).
(4) A small snack is permitted (Ibid 431:6).