A fundamental question arose concerning the essence of the mitzva of removing the ḥametz: is the mitzva essentially to eliminate the ḥametz actively or is the main principle that no ḥametz remains in a Jew’s possession?
According to most Rishonim (Ramban, Maharik, and others), the mitzva is primarily that one’s domain be free of ḥametz. One who has ḥametz must clear it out, and one who has no ḥametz in his possession has fulfilled the mitzva by having no ḥametz in his domain.
However, some Rishonim (Tosafot, Ran) imply that only someone who has ḥametz becomes obliged to fulfill the mitzva, and he fulfills it by clearing the ḥametz out of his house. One who has no ḥametz is exempt from the mitzva. Yet even according to this approach, we do not find that the Rishonim recommended acquiring ḥametz in order to fulfill the mitzva of removing the ḥametz. Nevertheless, there are Aḥaronim who wrote that it is appropriate for one who has no ḥametz in his possession before Pesaḥ to go beyond the letter of the law and buy some ḥametz, so that he may fulfill the mitzva of removing the ḥametz according to those who hold that one must actively remove ḥametz.
In practice, Jews are a holy people and strive to enhance the mitzva by making sure they have ḥametz in their possession on the 14th of Nisan, with which they fulfill the mitzva of eliminating ḥametz in a manner that satisfies all views. Moreover, they are so scrupulous as to remove the ḥametz specifically by burning it, for, according to many poskim, burning is the preferred way to destroy the ḥametz (see below, 5:4).
I wrote that fulfillment of the mitzva requires a kezayit because according to many poskim the requirement to eliminate ḥametz applies to a minimum of a kezayit (see MB 442:33). Even according to those who adopt the stringent view that less than a kezayit must be eliminated, it stands to reason that this is only so that one does not eat it and violate the prohibition of eating ḥametz, which applies even to a piece smaller than a kezayit. According to the overwhelming majority of poskim, however, there is no Torah prohibition of bal yera’eh and bal yimatzei on a piece of ḥametz smaller than a kezayit. So state Dagul Me-rvava §442, Ḥakham Tzvi §86, and Sha’agat Aryeh §81. According to many, the mitzva to eliminate ḥametz is linked to the prohibitions of bal yera’eh and bal yimatzei. (See below, 5:4, n. 3, which discusses how some are careful not to pour lighter fluid on the ḥametz at the time of burning, whereas others maintain that this is not an enhancement of the mitzva.)