As we have learned, in addition to bitul ĥametz, the Sages ordained the active elimination of all ĥametz remaining after breakfast on the morning of the fourteenth, and any ĥametz that was found during bedikat ĥametz (including the ten pieces of bread that were hidden before the search). In principle, one may eliminate the ĥametz in various ways: by crumbling it and throwing it into the wind, the sea, or a river (SA 445:1); by pouring bleach or some other substance on it, rendering it unfit to be eaten by a dog, since if it is not considered ĥametz food, it need not be eliminated (SA 442:9); by placing it in an ownerless public domain before it becomes forbidden (MB 445:18); or by flushing it down the toilet, whereby it no longer remains in the house.
Nonetheless, the holy people of Israel customarily enhance the mitzva of eliminating the ĥametz via burning it. Nothing eliminates ĥametz better than fire. Furthermore, there are poskim who maintain that the mitzva to dispose of ĥametz must be fulfilled by burning.
Those who wish to enhance this mitzva further must make sure to nullify the ĥametz after burning it, since if they nullify it beforehand, the ĥametz will no longer be considered theirs, and they will lose the enhancement of bi’ur by burning. One must therefore be careful to leave enough time after burning the ĥametz to nullify it, for after the fifth hour of the day it is no longer possible to nullify ĥametz (as we learned above 3:6). Hence, as soon as a kezayit of ĥametz has been burned, the enhancement of bi’ur ĥametz by burning has been achieved, and the bitul can be recited.
Some people, when using kerosene to light the fire, are careful not to pour it directly on the ĥametz. They do this so that the fire alone destroys the ĥametz, and the kerosene does not render it unfit for consumption by a dog before it is burned.
. There is a dispute in Pesaĥim 27b regarding the mitzva of destroying the ĥametz: R. Yehuda says it must specifically be burned, and the Sages say it can be destroyed in any fashion. According to the majority of Rishonim, including Rambam, Rosh, Ritva, and Ran, the halakha follows the Sages; this is also the ruling of SA 445:1. A minority of authorities, including Tosafot and Sefer Mitzvot Katan, follows R. Yehuda. Baĥ and Gra add that even the Sages believe that the preferred method is burning, just that it is also possible to destroy the ĥametz in other ways. Other Aĥaronim disagree and feel that according to the Sages there is nothing special or preferable about burning, and one may destroy his ĥametz in any way.
Most Rishonim feel that even according to R. Yehuda, the mitzva to burn ĥametz only applies to ĥametz that is left over past midday of the fourteenth, when it becomes forbidden, similar to the law of notar (uneaten portions of a sacrifice left over until the morning), which must also be burned. However, before midday of the fourteenth, it is possible that even R. Yehuda would agree that one may destroy the ĥametz any way he wants; this is the opinion of Rabbeinu Tam and Maharam Halawa. On the other hand, Rashi explains that according to R. Yehuda the mitzva is to burn the ĥametz before midday. According to Rosh’s understanding of Rashi, the mitzva to burn the ĥametz only applies during the sixth hour of the day, but according to Tur’s understanding of Rashi, the mitzva to burn the ĥametz applies even prior to the sixth hour. If this opinion is correct, the mitzva to destroy the ĥametz is specifically by burning it. See Birur Halakha Pesaĥim 27b for a summary of the topic. Even though it is clear according to almost all poskim that there is no mitzva to burn the ĥametz before it becomes forbidden, Rema 434:2 and 445:1 writes that the custom is to burn the ĥametz even earlier. See Or Le-Tziyon 2:33, which explains that the stringency of burning the ĥametz is dependent upon the combination of several opinions: firstly, the authorities who follow R. Yehuda; secondly, Tur’s understanding of Rashi that the mitzva to burn the ĥametz applies even before the ĥametz becomes forbidden; and thirdly, Tosafot’s opinion that the act of nullification renders the ĥametz ownerless, as opposed to Rashi’s understanding that nullification accomplishes the mitzva of destroying the ĥametz (and thus the only way to fulfill the mitzva of destroying the ĥametz according to Tosafot is by burning it). See also Bedikat Ĥametz U-vi’uro 7:5-7 and Hilkhot Ĥag Be-ĥag 8:7-8.
It is also worth noting that, according to a simple reading, the mitzva of removing ĥametz (in Shemot 12:15) is to dispose of the ĥametz before it becomes forbidden, as most Rishonim write. Ran and Ritva also write that one fulfills this mitzva by conducting bedikat ĥametz. Rambam writes that the mitzva of removing ĥametz begins on the night of the fourteenth (MT, Laws of Ĥametz and Matza 3:1). However, Rosh maintains that the mitzva only begins once the ĥametz becomes forbidden. Hilkhot Ĥag Be-ĥag 8:8 summarizes this topic.
Sidur Pesaĥ Ke-hilkhato 15:4 states that one should be careful not to pour lighter fluid on the ĥametz itself, and see Hilkhot Ĥag Be-ĥag 8:10 n. 17, which disagrees, since the main objective is to turn the ĥametz into ashes, regardless of whether or not its taste remains intact. See above ch. 3 n. 8.