The search for hametz takes place the evening prior to the 14th of Nisan, but one is allowed to continue eating hametz until mid-day. The Gemara teaches that hametz is Biblically forbidden beginning at noon on that day. A baraita is brought that suggests a number of different opinions regarding the source for this halakha, all based on the passage (Shemot 12:15) akh ba-yom ha-rishon tashbitu se’or mibataikhem – “but on the first day you should destroy the leaven from your homes.”
Rabbi Yishmael asks – how do we know that the “first day” mentioned in the pasuk refers to the day before Pesah? Because of the passage (Shemot 34:25) that teaches “do not slaughter the blood of my sacrifice on leaven” meaning that the korban Pesah, which is prepared on erev Pesah, cannot be brought at a time when leaven is still permitted.
Rabbi Akiva teaches that the first day must mean erev Pesah, because work is forbidden on Yom Tov as it is on Shabbat. Given that burning is one of the forbidden activities, how can we burn leaven on Yom Tov? So the command to destroy hametz on the first day must refer to the day before Pesah.
Rabbi Yose argues that the word Akh in the pasuk implies a division of the day, so that only on part of it will hametz be forbidden.
Rava learns three basic rules from Rabbi Akiva’s teaching –
the appropriate method for destroying hametz is burning
the passage that teaches about fire as prohibited on Shabbat emphasizes that every forbidden activity of Shabbat is illegal in its own right
although making use of fire on Yom Tov is permitted for activities like cooking, it is not permitted for other purposes.
Of the 39 types of activities that are forbidden on Shabbat, burning (i.e. making use of fire) is unique in that it is the only one specifically mentioned in the Torah. At the beginning of Parashat Vayakhel we are taught “Six days you should work and on the seventh day you will have a holy Shabbat to God, whoever works on that day will be put to death. You should not kindle fire in the places that you live on the Shabbat day.” In an attempt to explain why this particular melakha deserves special mention, some tannaim say that it is unique in that its punishment will only be that of a lav – a simple forbidden act – whose punishment is malkot (=lashes), rather than a death penalty. Rabbi Akiva in the baraita that is quoted in our Gemara takes a different position. According to him it is separated from the others in order to teach that each one of the melakhot is forbidden on its own, so that the individual who transgresses the Shabbat does not need to perform all of the forbidden activities in order to be held liable. Transgressing even one such activity is enough to be punished.